The old XP warhorse was seriously low on disk space so a bit of TLC was required.
Warning: This worked for me - you're on your own! Backup important stuff first!
Just get it dude!
Then run PC Decrapifier. This didn't do much in my case but then I'm quite strict on what I install in the first place.
Then, using Explorer Search, I searched for *.log, *.tmp and *.bak and deleted all the junk.
Then I searched for all files greater than 10 Mb and deleted all the junk.
Advice: If in doubt , don't delete.
Then I deleted the old "Windows Update" files. These are the ones in the /Windows folder in folders like "$NtUninstallKB842773$". Again, Google this if you're not sure.
Then I deleted the files in the /Windows/Prefetch folder. Again, Google this if you're not sure.
If you have SQL server installed, you can clear out most of the files on the C:\Program Files\Microsoft SQL Server\90\Setup Bootstrap\LOG folder. Again, Google this if you're not sure.
And then run Windirstat. This gives a graphical representation of who is using what. Poke around a bit.
Man, I had a ton of crap on my PC and now it's gone!