SERIOUS help needed computer malfunctioning

[acidslice]

OK, to start i bought the entire system form yoyo, in the shop, with advice, very helpful and awesome knowledge. I have had my fair share of problems with non activating ram on a striker and my razor keyboard not being compatible with striker and mobile N! card not being compatible with VISTA,

but the most serious of problems is at hand and driving me crazy...

PROBLEM:
the system freezes, the picture remains but nothing works, the lcd on the mobo just displays the timer still counting. This occurs while playing non-demanding games WC3, and even sometimes simply browsing the net or while watching videos.

THINGS I HAVE TRIED:
memtest on 2gb and 4gb separately, both came out clean
New hard drive, and hence a new vista install with no programs installed at all.
2 separate asus bios installs, set to standard with no OC

THOUGHTS:
all i can put it down to is a faulty PSU or a faulty gfx card, is there a way to tell, or can yoyo lend me a supply and card, or can i pay to rent one, all i ask asking for is a system that is stable

MANY THANKS in advance


SYSTEM:

1000w pro coolermaster psu
xfx gtx8800 ultra
zalman gt1000 case
zalman processor fan
8500 4X1GB corsair ram
e6850
striker extreme
icy box card reader, unplugged dutring testing
dell 24 screen with hub
raptor 150 gb
and seagate 500gb

[acidslice]

I am also running a powerline networking solution, bought from yoyotech, netgear hdx101, don't know if this is usefull