Mobo fail
Strange thing just happened. I have installed Win XP over Win 7, which caused boot menu to corrupt - I could boot only XP’s, so after a moment of googling I’ve found EasyBCD - great and simple boot manager. Using it I restored Vista bootloader on the primary partition of first HDD, rebooted and the screen went black.
WTF, I thought for a moment BIOS had died again (remember my problems two months ago?) but then the computer boots, the HDD LED blinks vividly, so it’s running with no video. Then I thought ‘VGA dead’ with a smile - I would replace the crappy GF8500GE with something newer (HD4770/4830/4850 or GF9600GT/9800GT/GTS250), even started looking for warranty card. I even digged out some old S3 Virge PCI VGA which proved some of my theories - using it I saw the computer booting (bootloader was installed correctly), but then came the idea ‘what if I switch PCI-Express slots’.
Damn I hate those moments of truth.
Anyway, I put the 8500 in second PCI-Express slots, and it worked! Seems like the first (PCIEx16) slot went down to hell, so I quickly changed the configuration of PCIE slots from 16/2 to 8/8 (damn you DFI for those jumpers), reseated the VGA in the second slot and off we go.
Good thing is that I realized this could be the cause - I would spend money but the problem will be there still.
Bad thing is that I don’t know why and how this could be reverted.