System Restarts without warning!

[P1990]

My system with the following specs:

P4 2.00Ghz(FSB 400Mhz)
Gigabyte Motherboard(VIA chipset)
256mb 64bit XFX 6200 AGP 8X card in 4X slot
40Gb Seagate HDD
1GB memory(purchased only a few hours back)....333Mhz module...while the motherboard supports only 266Mhz...
my system suddenly restarts without any warning and neither does it display that it experienced some problem once it restarts!...What could the problem be?'
I have attatched 2 dmp files...please help me out because i constantly keep losing my work..

 

[Whiffen]

Power supply's are the most likely culprit for random restarts. Make sure its not running to hot as well.

 

[P1990]

The PSU is 6months old....i had actually had got the faulty PSU replaced......

 

[Whiffen]

Doesn't mean its still working ;d Do you mind telling us about your PSU? Wattage, brand, amps on the 12v rail. You would need about 300 Watt minimum and 18 amps on the 12v rail.

 

[woody1191]

Mini070308-01
BugCheck 1000008E, {c000001d, bfbd4c05, baf1f99c, 0}
Probably caused by : nv4_disp.dll ( nv4_disp+201c05 )

Mini070308-02
BugCheck 10000050, {ff9a92ac, 0, bf8152f0, 0}
Could not read faulting driver name
Probably caused by : win32k.sys ( win32k!xxxRedrawWindow+50 )

RAM and HDD can cause these restarts as well.
You could try running Memtest first and then run your HDD manufacturers Test.

Bugcheck 0x50 can be caused by defective RAM or incompatible software.