Sometimes no audio/video post on system startup

I am experiencing a problem with my newly assembled system and am hoping someone here would be able to shed some light on the situation.

My setup:
Intel Core2Duo 1.83ghz Allendale
(boxed, so with original cooling)
MSI P945L Neo mainboard
Asus Geforce 9600GT
2GB Nanay Elixir Cas5 DDR2-PC6400 (2 strips of 1 gb each)
Coolermaster 320W PSU (20 pins connector)

The problem:
My system is showing irregularities while starting up. It will start up fine and run without noticable problems, but sometimes it will not give any video/audio post on boot.

When it does not give video, it makes no sounds whatsoever, but everything else is powered on, casefans/cpufan/hdd/all leds etc.

When it does give video, it makes a sequence of 3 beeps at bootup, which I have not been able to figure out with the manual what they mean.

The system will never give video after a soft reset, so if windows xp tries to restart during software installation for instance I am left with a blank screen, whereas with hard resetting I sometimes get video again, sometimes not.

The GPU was tested on buying in a similar setup and was diagnosed to work fine at the time, so I guess I can rule out a fault there. The GPU is also sitting securely in the PCI-e 16x slot. Removing it and reinstalling did not resolve the problem.

As the system still gives me a good boot sometimes I am leaning towards either faulty memory or a problem related to the PSU. The voltage delivered seems to be fine on all channels, but might it be possible that this problem arises from having the PSU connected with a 20 pins connector to a 24 pins connector on the mainboard?

It seems that somehow holding the powerbutton for a longer while before releasing gives me more succesfull startups also.

I'm not all that technical, so I would very much appreciate any light you could shed on the situation.

Thank you in advance,
Krysta

The problem does sound to me to be your psu not providing enough constant power to your components.

Do you have another or could you borrow one from a friend to try?


You do have the additional 4pin power plugged into your board?

Yeah,came to the conclusion it had to be the psu after testing most of the other components in a different system and it all worked like a charm.

The separate 4 pin plug is connected as it should be.
Problem is that my psu only has a 20 pin atx plug which is plugged into the 24 pin connector on the mainboard. In theory that should work, but seeing as I'm having stability issues, I'm not going to take any changes. My other psu also only has a 20 pin plug.

Also while the opther psu is a 400w instead of a 360 like this one, it only provides 12A on the +12V line while my current psu does 17A.

I checked out some additional info on the forums and it turns out that the MSI mainboard I'm using needs 18A on the +12V line to ensure system stability (according to MSI). So my psu seems to be a bit on the low end in general.

Thanks for your response, I'll buy a new psu next week and will post here again if that solves the problem. I'm on a tight budget though, and looking through the lists of reputable psu suppliers it's kind of hard to find one that actually supplies more then 18A on the +12V line while still remaining slightly affordable.