Motherboard doesn't detect GPU

Fanax

Honorable
Apr 5, 2016
65
1
10,545
My PC at work:
460W
Foxconn G31MXP
Intel® Core™2 Duo Processor E6750
A-Data DDR2-1066+ PC2-6400 x 2 (2GB)
Western Digital WD800JD-75MSA3 80GB

Integrated card works well, no issues there, but when I try GeForce 8600GT it can't detect it. I tried changing BIOS settings (also updated to most recent version) to make 8600GT primary, but with no luck.
I found this video https://www.youtube.com/watch?v=mMRYKmp0HBY, so does it say, that MB and GPU are incompatible?

Any suggestions?
 

Fanax

Honorable
Apr 5, 2016
65
1
10,545
I tried GeForce 8400GS and it worked flawlessly... I thought that my 8600GT died, but installed it to other PC and everything worked. What sorcery is this?