Hmm,

At this point I'm inclined to think that this is a hardware problem, either a bad drive or bad controller. I've seen similar on T20 of that vintage. In the end, the owner just stopped using it , except as you are doing now. It seemed to me that the connection (the bus) was flakey. Intermittently working, then not. If it is the controller or a connection problem then the purchase of a new drive would not be worthwhile.

Knoppix is a great way to get some more use out of the old lappy, enjoy!