PC crashes when it gets to the ALU performance test

I put vista premium on a DFI-Ultra board. It installed fine but when
as it tries to evaluate the ALU performance to figure out the
experience index it crashes to a blank screen. Then a second or two
later the montior says no signal. The pc is still on but it never
comes back and when the system reboots is tells me windows was shut
down unexpectedly. But the error reporting service never pops up with
a promt to upload an error to MS.

I have the latest NVidia drivers for the PCI-E 6800. Now the video
card works well for the media player visualizations and Valve's peggle
extreme. But when I try Team fortress I get a flashing black screen,
messed up audio and the only way out is Ctrl-Atl-Delete.

I flashed the latest bios with no effect.

I moved ram around and have it down to 1 stick of ddr 400.

Becasue the fan burnt up on the northbridge I had to replace it and
now my video card has to run in the second slot because Fry's only had
one cooler and it blocks the main pci-x port.

I have a new seasonic PSU rated for 600 watts, one sata drive and one
eide DVD rom.