Not being a computer expert or anything, but I was told by someone who knows that if your hard drive goes above 1% fragmented, hit the defrag button.
Windows 95 tells us, well it tells me, that I do not need to defragment at this time. My friend told me to ignore that message and defrag on a regular basis.
Microsoft's Internet Explorer 5 automatically emptys your temporary internet files for you at the end of every session if you want it to.
I don't know how standard a practise this is among browsers, but it saves even more un-necessary clobber squeezing the life out of your disk space.

Bren.