Cleffer

In my experience, using explorer does not work accurately to determine drive space. I'm not sure where the issue is (seeing all files? buggy? drive partitions?,) but I've seen one before with some computers and I don't use that as a judge. I would trust the My Computer as the best tool for an end user because it takes *all* space into account.

Are you certain that you don't have a hidden partition on the drive (ie for an OS installer or something similar?)

What I would do (and not saying that it's the most effecient method by any means) is sit back some night and figure out where all my space is going. I'd invest in an external storage source such as a USB drive or the like and move all non-pertinant files (music, pics, docs, etc) over to the external source. This would not only gain/save space, but put your memorables in a safer location in case of HD failure. if you're HD is anything like mine, you'll gain half your drive back. :D

Hope that helps.