Continual but inconsistent failure to boot

(I'm 75% sure this is a power supply issue, but I am quite stretched for money at the moment and so want a second opinion before I purchase a new one.)

The Computer:
I've had a custom-built PC since early 2007. Except for a new graphics card, I've made no other changes until August of last year, when I bought a motherboard and processor from a friend, both reportedly new. He says he never OC'd it. At the same time, I bought two fresh sticks of RAM. My current setup is such:

AMD Phenom II X4 955 (@3.2GHz) (Bought used)
ASUS M4A89GTD Pro (NOT the USB3 model) (Bought used)
2x2GB Sector5 DDR3 1333MHz sticks (Timing:9-9-9-24) (Bought new)
SAPPHIRE 100293L Radeon HD 5570 1GB 128-bit DDR3 PCI 16x
Antec NeoPower 550 550W ATX12V (Bought new few months before)
Western Digital 150GB Raptor Drive
Seagate Barracuda 7200.9 ST3500641AS 500GB
LITE-ON 16X DVD±R DVD Burner
Generic CD-RW/DVD Drive
Antec Performance One P180 Silver Computer Case (Which I doubt matters, but include for the sake of completion)

The PSU Calculator puts me at 369, so 550W should be enough.

The Background:
I've recently moved from Texas to Colorado by way of Iowa. I took this computer with me for fear the movers would break it (haha). During this I moved it in and out of my car, worried about theft (and to move things around), before arriving at my Grandpa's in CO. I stayed there for about a week, during which time I used the computer. When I first set it up I plugged it into an outlet that (unbeknownst to me) was controlled by an analog (slider) switch that also controlled the ceiling lights. After turning it down and seeing the PC shut down, I switched the plug to one that didn't shut off. Trying to boot it up right afterward had no result, so I turned off the power supply, checked the power cable, turned it back on and it booted just fine.

The Problem:
At the end of the week I moved it to the place I'm renting. At first it started just fine, but after two or three days it would have problems booting, eventually failing to boot completely. The MemOk! light would come on, and after turning the PSU off and on, I'd hold the MemOk! switch and the computer would come on, report that it had fixed the problem, and happily boot. Then when I tried to save the BIOS settings or boot the computer normally, I'd hear a quick click of the CPU fan, the case fans would come on, and nothing. At one point it reported CMOS problems; a change of the battery took care of this.

When I was able to get it to boot I ran MemTest on the memory, found no errors (only ran one full test). I've run chkdsk on both hard drives with no reported problems. (This was on another machine; trying to run chkdsk at boot on this PC caused BSOD.) I've tried to boot the system with nothing but the PSU in (the MOBO has on-board video), same thing. I got frustrated and just set the whole thing aside. MemOk! started to fail at booting.

Today I went ahead and took it apart 100%. I had taken it apart before, but left the motherboard and other things in the case. Now it's all out. I took the MOBO w/CPU, one stick of RAM, and the Raptor drive, set them aside, hooked them up to the PSU, and tried to boot.

And it worked. Subsequent tests have shown me that I can boot even from the power button only if I turn the PSU off, wait ten seconds, turn the PSU on, wait ten seconds, and hold the power button for more than two seconds but less than four seconds. So far this seems fairly reliable. Doing a proper shut down of the system will not allow it to start back up without first turning off the PSU.

My main thought is that the PSU is failing (it is almost five years old now, and the computer is running 70% of the time), but another thought is that during the last move I did something to the Motherboard that gives it iffy power connection at first. I'm behind in a few bills (but will be caught up by the end of the month thanks to my new job), so I'd have to hold off buying anything new

Is there anything else I can test or try before I (wait to) buy a new PSU? Right now it's running on the barebones setup mentioned before, with a wireless USB dongle and a USB Keyboard/mouse hooked up to it, so I can run any tests suggested.

While it is not beyond realms of possibility, I wouldn't bet that the problem is power supply. I would bet that some hardware component or connector has been loose, which would explain intermittent symptoms.

From what you have described (replacing motherboard, processor, RAM and later moving the system) it is a distinct possibility that you loosened one or more connectors.

All that you have demonstrated by booting with a subset of your components is that those particular components might be alright.

Try putting your whole system together, one component at a time, and ensuring connectors are firmly seated.

I've taken it apart to at least some extent about five times now since it stopped working (and reseated cables many more times), so I can't see that being an issue.

But with this new theory about powering up I'll do just that and add piece by piece. If I can continue to boot after each piece while applying the power theory, that will prove it's a power supply issue (my thought is that the power supply capacitors are wearing out and take longer to fully charge, which is why after plugging it in I have to wait, and why after shut down they dissipate and can't charge up again for some reason).

You can manually power-on a power supply without connecting it to anything else by shorting two of the pins in the main plug that normally goes into the motherboard as shown here: http://www.youtube.com/watch?v=u0OKmIuNtmI&feature=related

Obviously given the nature of a power supply you must exercise caution when doing this.

If the power supply exhibits problems when you're powering it on in this way then there is definitely a problem with it.

However, the absence of problems when testing it in this way does not indicate that there are no problems with it, since the problem may only exhibit itself when the power supply is under load.

Okay, I've been adding piece by piece back onto the Motherboard, booting after every addition. To recap, I had:

CPU
1 RAM Stick
Main Hard drive

In order, I added:

Second RAM stick
New DVD burner
Old CD burner
Video card

Everything was looking good up until the video card. Waiting ten seconds after turning the PSU on, I could boot to Windows just fine. I also found that if I shut it down normally and waited ten seconds I could boot it up again without having to toggle the PSU. But if I tried to power it on again right away after it turned off, it would never boot until I toggled. During boot up the Memory error light would turn on for two seconds twice.

Once I inserted the video card, nothin'. The fan for the CPU would turn on as if it were going somewhere, but the Memory light would come on, stay on, and that was that. I then removed the two CD drives, second stick of RAM, and tried to boot it up again. Success! It then went through the Windows Startup Recovery utility, which it went through once the first time I booted it while doing this. However, that time was rather short, and this time took quite a bit. Still, in the end it was able to boot just fine (though the AMD driver has problems, but that's easily remedied).

I took the power drive off and did as you suggested, E-Oreo. And when I started it I heard... nothing. The fan was barely moving air and no other noise came from the power supply. There were no stutters or anything else to indicate an interrupt.

I hooked it back up, made sure it powered up. Then I tried the second RAM stick. And it booted. Then I tried one CD drive. And it booted. Then I tried both CD drives. It rebooted during boot. Oh well, I thought... and then it did something odd. It restarted just fine. And booted just fine. So now it's running with everything sans case fans and the second hard drive.

So now I'm majorly confused. I still think it's a PSU issue and I just got lucky. Gonna try shutting down and booting a few times to see if it holds or not.

One thing I did change was to take the jumper out of the old hard drive (doesn't have instructions on the case, but I assume it's to ID it as the primary), but I don't know that it would make a difference.

I even updated Windows and it restarted just fine. Then I shut down and turned off the PSU. Each of the following had the PSU toggled between tries

1) CPU fan spins up then down. No boot.
2) CPU fan spins up then down. No boot.
3) Starts up, freezes during Windows boot
4) CPU fan spins up then down. No boot.
5) Starts up, freezes during Windows boot. I noticed this time that the booting screen (the flying colors to form the Windows logo) stutters before freezing.
6) Starts up, freezes during Windows boot
At this point I remove one of the the hard drives.
7) CPU fan spins up then down. No boot.
8) CPU fan spins up then down. No boot.
I plug the drive back in for kicks and giggles.
9) Starts up, freezes during Windows boot
Unplug again.
8) CPU fan spins up then down. No boot.
Unplug other CD drive
9) CPU fan spins up then down. No boot.
10) CPU fan spins up then down. No boot.
11) CPU fan spins up then down. No boot.

I think what happened before was a happy fluke. During all this I moved no other cords, touching only the PSU switch, the CD drive power slots, and the power switch.

So I'm pretty sure it's the PSU now, unless anyone else has other ideas.

If you're able to get into the BIOS at some point you can probably find an approximate reading of the rail voltages to see if they are significantly above or below where they should be.

I didn't quite follow what you did, but if it started failing after you added more components it might indicate that the power supply is not able to provide sufficient power. RAM uses practically no power, but hard drives and your video card might depending on what type you have.

I've looked at the readings before, they were all slightly below the stated voltage (like the 12V line read 11.57V or something). Never more than a volt below what it should have been. I'll go back in and get the precise readings if you think it will be helpful.

Yeah, I kept adding more components, trying to boot between each component. It failed when it got to the video card, likely the second most power-intensive component (if not first).

I've replaced the Power Supply (more power, but not as spiffy; no modular cords), and now I have no problem getting the computer to boot and display.

However, I'm still getting lots of crashes with Windows. The OEM disk (Win7 Home 64bit) I have doesn't seem to offer any kind of repair install to see if that will work. I'll get blue screens when starting and when trying to run Startup Repair. The system will randomly freeze completely, although this has happened only a few times now. It will freeze all the time when I try to plug in my cell phone, though. I can boot with it plugged in just fine. Taking out a stick of RAM can make the BSOD go away, but I can plug it back in and it will boot fine.

I'm worried that when I turned down the dimmer switch (unknowingly) connected to the outlet my computer was connecting to, it did a "brown out" of sorts and did electrical damage. Most in the PSU, but possibly some in the motherboard and RAM as well. I have one stick of RAM out now, I'm going to run it for a while and see if it starts to wig out.

I hope that I can figure out an exact cause, I'm behind on bills and don't have the money to buy a replacement motherboard, RAM, and (maybe) processor. I'll try putting the stick back in before bed and running MemTest again overnight to see if it will catch anything.

Well, what errors are you getting when you get the BSOD? That can help in pinpointing the remaining errors you may have.

You may need to do a reinstall of Windows, it's very possible that some of the data on the drive was corrupted.

Compared to the rest of the computer, RAM is pretty "dumb" electrically. That's why it's not hard to find memory with a lifetime warranty. This also tends to make it relatively resilient. It's certainly possible, but I'd be surprised if you damaged it.