Hmm, it appears that something called "pagefile.sys" is taking up the most room. I should just delete it. Oh, and those really large ntldr and ntdetect files are taking up a bit of space as well. They'll have to go
That's a neat trick, though. I enjoy learning "new" DOS commands.
If you actually notice your hard disk getting slow, and you're not just talking about the usual hardware-becoming-obsolete feeling, maybe it's time you defragged? I just got around to doing it on my machine yesterday, and nearly all the space on my two disks was fragmented.