System reboots unconditionally

I have problems with this config:
- Asus P5GC-MX/1333
- Ram: Kingston 1GB
- Graphics card: 8600GT
- Pentium D 946 3Ghz
- PSU MAX IN POWER 650W

You'll say I do not need 650W for parts but I think I'll buy the goods when they will come!

That's my problem, I have reboots from time to time unexplained since sometimes I do nothing other than Mozilla Firefox (some tabs but that's all). Sometimes it's in a game, not each time very greedy.

I change my psu six months ago because of the same problem, but it did nothing. I thought it was RAM so I also changed but did nothing either.

I can not find the reason and this annoys me a lot. Can anyone explain me why my system reboots unconditionally?

What is the model of your power supply? MAX IN POWER and heden is the same group then the fat shit that provides 200 W.

It may come from your power supply who is a big shit 150W with a label "650W" above, which do not meet any safety standard and provides tension pitiful.

Change this for a REAL power supply, worthy of the name, Corsair 400W CX will be ample and more powerful than your current mock-power supply, since it is really the power announced.

It is true that I saw on the test that a Heden is something not to say a fireworks!

So a corsair's what I thought to myself but what CX400W is sufficient to welcome an E8400 and a Hd4890/Htdi with a hdd Caviar T1 (config my future as I in two months time tenders)