I've got a smallish C: drive, about 140G, but noticed that in the last week or so I'd had only 200megs free. Not cool. A few hours later, I have 84.4G free. Here's now:

    * vsp1cln.exe - After you install Vista SP1, it leaves around the original files so you can uninstall the Service Pack if you want. After a few months with the Service Pack, I've decided for myself that it's a good thing and decided I don't need the option.
      Open up an administrative command prompt. That means, click the Start Menu, type cmd.exe, then right-click on it and click "Run as Administrator." Alternatively, you can press Ctrl-Shift-Enter to run something as Administrator.
      Next, type "vsp1cln" at the command prompt. If you select yes, you'll get back around 2 to 3 gigs. The only thing, again is that you can't uninstall SP1.

      VSP1CLN
    * Disk Cleanup - It's amazing to me the number of people who DON'T run Disk Cleanup. It's even better in Vista. Just run it. Often.
    * Disable Hibernate - I have a desktop, and I prefer just three power states, sleeping, on or off. I don't use Hibernate. Plus, I have 8 gigs of RAM, and hibernation uses as much disk space as you have RAM. From an administrative command prompt, type "powercfg -h off" to get that space back. Got me back 8gigs.
    * %TEMP% Files - Even though Disk Cleanup is great, sometimes for whatever reason it doesn't get