Before defragging, do a thorough disc cleanup.
Go to My Computer, right click on the hard drive icon, select ‘properties’ and Disc Cleanup.
Tick all the boxes except the first and the last then run it.
You could also uncheck the “Index This Drive For Faster Searching” box. The constant grinding you experience could be related to this - XP goes on indexing expeditions when the computer is otherwise idle and rarely allows the hard drive to spin down for very long - which has been attributed to premature hard drive failure but there don’t appear to be any hard facts to support this theory.
On the second (tools) tab is defrag and checkdisk.
If you install Spybot Search and Destroy (Download.com) be sure that it IS Spybot Search and Destroy and not something that sounds like it - there is a secure shredder tool that will find and remove a lot of crap that Windows doesn’t seem to be aware of.
There ar also immunisation tools and a hosts list to download that will further protect from redirects and known ‘bad’ websites.
Avast is an excellent and free antivirus program that works with Vista as well as XP.
I second the vote for Ubuntu - I’m using it on this machine and also have an XP/Ubuntu dual boot machine and a Vista machine.
This is the most secure and easiest one to use and has no protection other than Ubuntu itself. It is also a damn sight faster than the other machines despite never being intended to be. Leaves the much newer dual-processor Vista machine at the starting blocks.
You should have little or no problems with drivers - USB stuff just works. HP printers seem to be better supported than others but I only have HP printers so can’t compare - they just work once you tell Ubuntu what you are usung.
The two biggest concerns are graphics drivers and Flash.
Nvidia drivers are now easily available and also easy to install - which was not quite the case prior to the release of 7.04 (Fiesty Fawn).
Flash is also now much more simple to install.
You will need a bit of hand holding at first but the support forums are the best I have seen.
Also Psychocats has an unofficial but very useful support and advice section that deals fairly specifically and admirably with the last two issues.
But it isn’t Windows, never forget that.