Encrypted HD, keyboard not responding in BIOS or elsewhere.

Disconnect anything you don't need one by one. all usb devices, printers, scanners, cameras, etc...
Then disk drives, floppy drives, cd rom drives, memory, until just PSU and MoBo.
All I can think to do then would be to reset bios and hope for the best.
If you can't access it, or manipulate it, its useless.

Upon further investigation it seems like my very old PS/2 keyboard is broken. Gonna borrow one from a friend and see if that works. Otherwise I'll try your tips, thanks!

Gee,
you said "I've tried three different keyboards (one PS/2) and all with the same result."

Yeah, well it actually seems like there was nothing wrong with my old PS/2 as my friends one had the same problem.

Anyway, I've sort of solved it for the time beeing, I decrypted the HD using my old computer and I can now get into the OS on my new one. But the old problem still persists. I still can't do anything in BIOS, the keyboard, no matter what type I use just refuses to work during boot.
It's not a problem right now but it will probably be quite a hassle sometime in the fututre, which is why i'd like to try and solve it sooner rather than later.
Is there anything I can do?