Warnar Boekkooi

AAAAh I'm going crazy Fixing this PC

Hey all,

I'm bizzy trying to fix a pc for a friend of me but i can't find the problem with the PC it hangs after playing like 4 minutes solitair or doing word for that time.
It aint the processor it's new and i allready tested it with a working pc.
It aint the Motherboard also tested that.
It aint the memory because i tryed serveral working RAM memory.
It aint the Harddisk tryed 3 diffrend HDD's.
It aint the DVD player because the error is there also if it is unplugged.
It aint the floppydrive because the error is there also if it is unplugged.
It aint the powersupply tryed 2 diffrend kinds.
It aint the graphics cart tryed to 2 diffrend kinds of PCI and one AGP.

Here is some more info about the PC:
Intel Celeron 2.4GHz (Boxed)
JetWay P4X400DBZ
Seagate Baracuda 30GB
RICOH MP5240A DVD+RW/+R
TOPELITE 400 MAX (by CWT) Model NO: ISO-230
Elixir 256MB DDR-400MHz-CL3
S3 Trio64V2/DX
Windows XP
Symantec Antivirus Corp 9

Hope someone has a clou because i'm getting onto the point of trowing it out of the window !!

Good Luck To All