> Thanks to everyone for the responses. In fact, I have a spare 500 GB drive
> right here, but my question really is, how much space do I need to have on
> the drive before I uncompress it?


You can't know unless you can identify the majority of the file types then
make a guess. As mentioned, media files tend to be uncompressable, so if the
drive is full of movies, jpg, and mp3, the compression process didn't
accomplish much.

Or, try selecting a pile of files, say a big folders' (10 GB) worth, and
move them to an uncompressed volume. Compare the decrease in size on the
compressed volume with the increase on the uncompressed volume, and multiply
that difference by the total size of the compressed data.

I don't know about Vista, but IMHO it would have been better hiding that
compression tool somewhere that non-tech users couldn't find it easily.

-John O