I spent pretty much all day yesterday reformatting my hard drive.
My laptop is about 5 years old now. It has a tendancy to slow down over time, as it gets choked up with God-knows-what. A bit of slowdown I can handle, but everntually it gets to the point where it will stop and think for a couple of minutes at random intervals. And I don't mean when I'm running a bunch of apps at once, I mean on one application at any given time. This tells me it's time to sweep the floor and start from scratch.
I say it took all day. This is bacuase first I have to make copies of all my important files and so on (RWEP vids etc). Then I format. Then I have to re-install all the tools and applications I use as standard, Microsoft Word, Vuze, Daemon Tools, codecs, zip programs etc etc etc.
It's a pain in the ass to be honest, but there is something vaguely cathartic about it too, like when you deep clean your room / apartment and throw away all the junk you've been storing. I feel cleansed.