Hi there,
I have a similar problem although my 'second' hard drive is from my laptop and is in an external HD case.
My problem was I had, on my desktop pc, win98se on my C: drive and the laptop HD, in the external case, has winxp. The laptop drive was not accessable as it didn't show up in 'My Compter' so I installed winxp on the C: drive and now the laptop drive shows up, as D:, in 'My Compter. I am able to open it but like 'Andrew' am unable to access folders under my user ID on the laptop hard drive. How do I boot from the D: drive? :(