He probably needs the drive to be accessed by Win9x or something, I suppose.
Ok, after re-reading this and paying attention, the problem is obvious, even though I've never used Partition Magic.
You need to decompress all compressed files on each partition you want to convert before you try to do the conversion. Here's how to do that:
1. Open a command prompt by clicking Start->Run and typing cmd then pressing Enter.
2. Type cd\ and press enter.
3. To uncompress all files on this drive type compact /U /S /I and press enter.
4. To repeat this on other drives, type X: and press enter, where X is the drive letter. Then repeat step 3.