Infected BIOS?

[Kalador]

Hi, please bare with me on this.I do not have any means of getting a HJT log, I refuse to plug any of USB stick between my clean machine and the two potentially infected ones ,and my CD rw is out of action.

I've got two computers from the same house, displaying almost identical symptoms. They both have different hardware configurations though. One is slightly older and uses an IDE cable for the HDD and the other uses SATA.You'll see how this is relevant in just a moment.

Computer A:The machine using SATA asks for a "boot device" on startup, and fails to find the HDD.However when I change the SATA port and start up the computer again it works fine for another two, maybe three restarts.Then the problem returns.

Computer B:The machine using IDE asks for a "boot disk" on startup and also fails to find the HDD.Since I unplugged and re connected the IDE cable its been fine. Whether or not its related or this computer just had a loose connection I don't know.

both Systems are running WinXp sp3 and both are AMD systems.Computer A is running Bullguard and that comes up clean.

I'm leaning toward a hardware problem, but I would like some second opinions.

Any help you can give me with the limmited information I've provided will be much appreciated.

[shelf life]

I dont know of any malware that can infect the BIOS. Virus yes, but i believe they just leave the machine in a unbootable state and are very rare, after all malware wants and needs a working computer if it is to be successful.
BIOS malware no doubt is theoretically possible:

http://hackaday.com/2009/03/23/bios-level-malware/