Should be noted I have very little experience with Dell's so there may be the easy and hard way to go about this. Here's a article here about doing it on Dell with a disc, It appears it wipes everthing and you'll have to reinstall all your drivers and software as well if you go through the disc install. I did few Google searches and a few pages mentioned a restore partition that contains an image of the factory install, that probably includes everything like the drivers and software.http://www.pctechbytes.com/dell.htm
Guess it depends on what route you want to take but personally I prefer the first, drivers are easy to get and install. Mostly you need to get the ones for the display and sound... On a fresh install like that windows installs a generic drivers for both sound and video disaply. You just have to go to manufacturers site and get the latest and greatest for full functionality. If that only does a fresh install of windows only the other benefit is you'll have very clean install without all the crap Dell load onto your computer, you then install any applications that you need/want.
Dell does has support forum, I'd look around there and elsewhere before deciding what you are going to do.
EDIT: one last note, make sure you have the XP installation KEY. You will most likely need this to reinstall, it can be found on various things. Manual, sticker on the computer...