After reading your last post - this definitely sounds like a hardware problem. On older Compaqs, they had a diagnostic partition on the HDD that also contained info needed by the CMOS. If that partition has been deleted, you have problems. Another thing to suspect is the MB. Sounds to me like you are loosing communications intermittantly with various system devices.

'Course now we've all given you half a million things to suspect and check out, and haven't nailed one down, but at least you're a little closer to a solution. (PS - I have worked on those older Compaqs, and let me tell ya; they won't withstand a 20ft drop. They just don't like that type of hardware testing...)