Computer Fails 2 -10 mins after boot

[panboy]

The computer ive been useing for some time Builtit my self, as started to just Power of and Reboot after a wile , never gives me enuph time to do any thing , and if i try to run a program/Game it crashes even quicker

Let see the Specs are
Amd64 3200/754
768 meges of ram /DDR-3200 1x 512 + 1x256
MSI Geforce 5600
MSI NEO7 Mother Borard
80Gig Maxtor HDD, 20Gig Maxtor HDD and a 250Gig Maxtor USB HDD
it has an old PSU that i Got with my P4 Computer , i think its only 300Watt But it had been Running this config for a bout a Year

And a buch of CD rom Drives , there all prety Crappy

Now ive had a few Problems. sometimes when i turn it on it just Frezzes at post just before it does the Mem Test , and then i Reset and it boots fine...

But now my Real Prob is it Reboots when i turn it on after windows loads , for maby 5 mins, now i reformated and tryed 3 Differnt Os's (WinXP,Win2003Srv,Vista) and striping the system down to just The
80Gig HDD
The Mo bo
The GFX
and 512 Ram
And CD-rom

but its the Same Problem on All the OSes i try, and i have No idea, and it doesnt Record an Error into Event Veiwer,or give a BSOD
Edit : ive also Run MemTest on bout my Ram sticks , over night... and my Computer dident Crash, I thought this was odd

Ive Bought a New Comp to solve this , but i wouldent mind keeping my old one , for doing less intensive stuff

[GX1_Man]

A replacement power supply is the best place to start for a lot of reasons. 300w is not sufficient for that hardware, even if it is fuctioning properly.

This is not the time to save pennies. A $12.95 600w is not the same as a quality 450w from a reputable maker - Antec, etc. If you don't spend at least $50, you risk failure of your system and possible damage to the valuable components.

People get consumed with watts, but the current on the 12v rail is much more important. Price, name brand  and weight are a good tipoff to what is inside.

[panboy]

So you Recon its The PSU as Well, Some one else sugested that as well, but i call'ed him a n00b and decided it Must Be all the Expencive parts i have that R dated , and must need new ones ^.^

I think ill go pick up a new PSU, My Room mate works in a computer shop now so i can get a good deal

My new system is going to be awesome ^.^(And also a horrible waste of Cash /Glee)

[panboy]

For your information I failed English and Dropped out of school

Do you know feel satisfied that I am stupid?

But I’m not sure what that has to do whit weather I can fix a computer or not

[GX1_Man]

Sometimes the perception of a person is more important than the actual characteristics which may not be readily known.

It may be akin to all of the shop teachers in my high school were missing some fingers. Made me doubt their ability to teach the safe use of power tools, you know?

[panboy]

Ah but GX1-Man The Contrary is true , The fact they are missing fingers shows they know Very well by Experience what not to do.

For Example i learnt not to import an "Entire" Old registry to a new computer because i wanted a game to work that id lost the CD key for.

Never Ever Do that, It Breaks Your computer i know