Speed up Win Xp

System Properties -> Advanced tab -> Performance -> Settings -> Visual Effects set to 'Adjust for best performance

Go to Start -> Cmd and in the command prompt type sfc.exe /purgecache. This command does magic, i had 780 mb free space, and after this command i had about 1Gb.

To save space go to C:\WINDOWS\Driver Cache\i386 and delete all the files. You can do the same with the files and folders from C:\WINDOWS\Downloaded Installations