Like many other people most of my "work work" for my day-job is on a notebook PC. It is a pretty nice one with a Core 2 Duo processor, 120GB hard disk, dual display support, and enough dedicated plus shared graphics RAM to make Vista look nice (3D Flip, etc.). Off to the side I have a nearly 4 year old desktop PC for "busy work" like writing weekly reports, filling out forms, email, etc. So, I've been quite puzzled why the free drive space on its relatively tiny 40GB hard drive (by today's standards) kept getting smaller and smaller until it was almost out of space the other day.
After poking around a bit, I decided to delete the Windows uninstall directories (which numbered in the many of dozens after years of Patch Tuesdays) and the \Windows\Temp directories (which also numbers in the many dozens). It took quite a while for the old PC to just delete the thousands and thousands of files (literally) from those directories. However, when it finished I found I had freed up over 10GB of space on the 40GB drive So, 25% of the drive had been literally filled up with useless junk files.
This may not be much of an issue with PCs with hundreds of gigabytes of hard drive space. But, if you have a small old PC like mine, take a careful look at the temp files on your system. And, be sure to backup your PC before embarking on an exercise like mine (lest you delete something you shouldn't by accident).