I have updated the bios. Put it into safe mode and tried. I have also tried putting it in a diagnostic mode. It works in the cmos screen but once you boot up into windows the keyboard through the PS2 port no longer works. I have tried a repair install of windows as well. I am running XP Home edition on a intel dg31pr board.
Never had that before..
Have you tried another ps2 keyboard?
Have you looked at Keyboards in device manager, and tried right click and update driver.. and go to properties and look there does it say working properly.. could be something there.
I doubt this is the issue but look there in in device manager at properties.power management and make sure it's not any checkbox about windows letting it power down automatically, is unchecked.
of course you could try usb as no doubt you know but it'd be interesting to know what's going on here.. or for you to get a ps2 keyboard working.. especially since it works in the BIOS! Very strange. Normally ps2 is very reliable and especially, if it works in the BIOS it doesn't stop.. strange..!