some other thoughts:
get a good file cleaner - and start removing stuff in temporary folders, especially temporary internet files. Thankfully, you're not using IE in this regard, as IE will hoard stoopifying amounts of temporary internet crap, and then hide it from you like a child who's stolen the cookie jar.
a good file cleaner will also look for duplicate files, but make sure to go over the list before just removing stuff; some "duplicates" aren't really duplicates at all, and just appear that way.
also, you can manually go through stuff as well, and remove files media files and the like you no longer need; also clean up a lot of the left over folders from removing applications. Although WIN will unistall them, folders and files are many times left behind.
turn off your HDD indexing service, unless you really, really need it . . . WIN will keep an on running list of where everything is located, in an attempt to find files quicker; but sadly, unless you do a lot of file searches, it really just slows the system down as time goes on.
Clean up your shortcuts within Start>Programs and clean up the number of icons and shortucts you have laying on the desktop, as well as the number of running applications that hang out in the taskbar; when WIN boots up, it checks the targets for all those shortcuts to verify that the application is still there, it can turn into a lengthy process when there's a ton of shortcuts laying around.
and these two alone will probably have the biggest impact on how your OS runs:
A good defrag application is a must; download the trial version of
PerfectDisk - it can optimize your HDD while defragging, and can also be set up to defragment the HDD pagefiles on your next reboot - which is an area most defrag applications can't touch
also, pick up a good registry scanner, and remove a lot of the erratum that collects in the registry as well (just installing and removing other applications will leave broken registry values) . . . also find an application that can defragment and compact the registry as well
and one last thing, turn off WIN XP's disk defragmentation service!!! here:
http://msdn.microsoft.com/en-us/library/ms932871.aspx This service chills in the background and will start to defragment your HDDs when the system is at idle or under low disk usage . . . problem being, is that 3rd party software does the job better, and WIN service will muck that up, and when your stored space starts growing, WIN service takes longer and longer to run, and in some instances doesn't like to relinquish control of the disk (it can't stop if it's in the middle of writing and copying files).
