Did the Word slow loading issue develop slowly over time or happen all at once? Has it been slowly getting worse or just stable bad?
Do you have all the service pack updates for XP?
Same for updates for Word.
Do you have the same slow load on other Office Products such as Excel that you have on Word?
What Anti-virus program do you have? Are you sure your system is virus free? I think there are some less well known viruses that inhabit Word - although they are not very prevalent - you will see what I mean if you google "MS word viruses"
Things you might try to improve performance if you have not:
1. Defragment with HD
2. Run disk cleanup - see this link:
http://support.microsoft.com/kb/310312
3. Run MS Check Disk utility - file structure problem might affect both the slow performance and files showing up again
http://www.microsoft.com/windowsxp/using/helpandsupport/learnmore/tips/kbtip.mspx
Word itself might be corrupt after all this time - one relatively easy step might be to uninstall and reinstall it.
I also suggest going to PC pitstop and running a free complete system scan and seeing if that reveals anything.
http://www.pcpitstop.com/pcpitstop/default.asp
Depending on what you find after that, other areas to explorer include:
1. Cleaning the OS registry
2. Purchasing a tool like Norton System Works or similar to fix problems and clean system
3. Revising the programs that load at start-up
4. Updating HD driver - although this usually is not required
You could also try re-intalling the OS (only after backing up all personal files) but it can be a laborus process as you would then need to reinstall all programs and input settings. And you might have special problems using the Dell support version - if that is what you have - and are out of warranty so they will not provide free assistance. Although a 5 year old PC can accumulate a lot of garbage.