Windows7 b. 7201 vanished keyboard!

Hello there guys.
The strangest think happened to my desktop PC after installing 7 build 7201: keyboard is missing during BIOS start, and I can´t access the BIOS setup! I installed it to see how things are going, and now, even after installing my good old XP Pro, keyboard is ALWAYS missing during BIOS post. It is activated only after system loads. I have tried serial, PS2 and USB keyboards, but it´s come to no good. I have to access setup for tweaks, and most importantly, to choose devices for booting up, like CD drive for Windows clean installs (when needed). I can only boot from CDs if I disconnect primary SATA HDD, because I´ve left boot order HDD and then CD-ROm drive. But it is a bummer to open case every time I have to do this. Never seen it in my entire life!!! Any clues on what is going on? Tips for having the keyboard again, back to life? I want to access my BIOS Setup, please!
Thanx in advance.

Mobo: Asus P5K-SE
gForce 8600GT
4GB RAM