|OK. then getting rid of the existing data will do you fine. |
If you have the Recovery disk set for it, re-load the original software.
If you don't, if you have or can borrow an OEM XP CD (It has "For distribution with a new PC only" or similar on it), of the same version, Home or Pro, doesn't matter what SP updates it has, but SP1 or later would be better, if it has a harddrive > 137gb / 128gb in Windows - then you can use the Product Key that's on the official label on the case to legally, as far as Microsoft is concerned, reinstall XP on it. After Setup has finished, Install the drivers for it, avalable on the Dell web site in the downloads for your model.
Whenever you load Windows from a regular Windows CD (or DVD) from scratch, after Setup is finished you must load the drivers for the mboard, particularly the main chipset drivers, in order for Windows to have the proper drivers for and information about your mboard hardware, including it's AGP or PCI-E, ACPI, USB 2.0 if it has it, and hard drive controller support. If you have a generic system and have the CD that came with the mboard, all the necessary drivers are on it. If you load drivers from the web, brand name system builders and mboard makers often DO NOT have the main chipset drivers listed in the downloads for your model - in that case you must go to the maker of the main chipset's web site, get the drivers, and load them.
Load the main chipset drivers first.
You could then use a program to write stuff to the unoccupied free disk space (a security wiping program) to remove all traces of what could otherwise be un-deleted if you're paranoid about that.