Crash and now no POST

I realize everyone asks this question, but it seems everyone's situation is somewhat unique, so here is mine.

The other night I was just using my computer (surfing the net, nothing strenuous) and my computer just froze (it didn't turn off or anything, just froze). I tried restarting it and it powers on but nothing else happens (fans spin up, drives light up, but nothing on monitor; it just sits in sleep mode). I tried reseating the ram, video card, and CPU with no luck. I have two sticks of ram and have tried putting them in different slots and only using one, so I'm pretty sure that's not the problem. The lights on my mobo light up (one LED and it is green) and the other components seem to get power (my cd-rom drive, HD spins up, and even my wireless card that's in a PCI slot flashes lights). I tried starting the comp with no ram and it beeped a lot at me. Unfortunately, I don't really have access to another computer to pop parts out and test them. I guess I am hoping to get some opinions on the problem, or ideas that I can use to narrow down the problem so i don't have to buy a bunch of parts (i believe it to be the CPU, mobo, or power supply (although i am thinking this isn't the problem, but you never know).

specs:
intel P4 prescot 640 3.2 Ghz LGA 775
ASUS P5LD2 Intel 945P mobo
COOLER MASTER eXreme Power Supply 430
OCZ Gold Series 2x1 GB SDRAM DDR2 667 Dual Channel Kit

Hi joec12 and welcome to Dev Shed.

Try re-setting the CMOS by removing the battery for a few minutes and then replacing. After which, see if the machine till boot, or even reach POST or allow you to enter the BIOS.

I have to say though, on first thoughts, it sounds like a failed CPU and/or mobo to me.

Yeah, I tried that stuff too. I guess I'm just down to trying to figure out which it is: CPU or Motherboard. Any tips on figuring it out without having another comp to swap parts with? Or maybe your best guess?

Personally, I would say that the CPU is the problem here, but there is always the chance that both the CPU and mobo are fried.

When a CPU fails, I usually always replace the mobo at the same time.

hi
dear friend use a diagnostic card u really get to know whats going on with ur mobo whether its really dead or alive .
all info is given by post codes on display.

If your PC is a nice $$ one, new, fast and whatall, then try and fix it.
if you can't find a friend who is competant to help you with h/w diagnosis, I would recommend spending $100 to $150 at a good PC shop to have them fix it.

If the PC is an old, slow junker, then this is a good excuse to buy some new parts or a new box ready-to-go.

Okay,
I was playing World of Warcraft at the time and I got up while I was healing to get a drink. When I returned everything was locked and the sound was extremly scratchy and repeating.. and then I hit the reset button on the front... it just went black and everything whirrd but no beeps or anything... so I clicked off the PSU and waited... turned it back on after awhile and it was the same... no beep.. nothing just the whirr of fans... she ain't talkin to me..

This is what I have:
Alienware A51 Case
Intel Socket 478 Mobo (don't have more info right now)
P4 3.06ghz 800mhz FSB
2x512 2x1024 DDR Ram
512mb AGP Nvidia Card
Sound Blaster Audigy 2
PSU 850w

Now, recently I changed out a few things because my comp was severaly out of date after 4 years.. if you can tell by the socket 478... I got the vid card first... it needed more power so I dropped my 420w PSU for a 850w PSU (was pretty cheap like 250 or so)... it worked great and I also bought 2 1024mb ram sticks... those worked great... everything was fine till the day it died (like two to three weeks after everything went in)... I've tried replacing the ram sticks that I bought with the old ones... I've tried booting it off 1-4 ram sticks in different slots.. I've tried resetting it with taking out the battery for 10 minutes... I even took off my heatsink on my CPU to see if the P4 was damage and then replaced the P4 because I thought I had it figured... I've tried changing out my video card with my old one.. I've tried unhooking my dvd-rom, floppy, and taking out the sound card.. I've tried doing everything above on both my 420w and 850w PSU.. I'm out of ideas and screaming for help. Someone I was talking to said my PSU is too high for the mobo that it probably fried it. Is it my mobo or is it something else?

Thanks