Once you have booted open a DOS box and type msconfig.
You will see a Startup tab which then lists all programs
that run when you start XP. Try "un-ticking" some of the
programs you don't really need (e.g. Quicktime,
Realplayer, Winzip ....). This may help. Remember to keep
your antivirus though
All you are doing is stopping loads of stuff appearing in
your System Tray(which takes time). You are not
uninstalling anything.
You should also run a defrag on your C: drive a couple of
times.