sorry work got busy and i lost you for a minute
unless they bought a retail version later, then both dells are OEM licenses
Product Key on MS sticker on side of Dell box (I'll call DELL-2) is not the key that Belarc Advisor listed with it's OEM license
then someone had reformatted this PC before and used another disk/COA....the license key on the side of that computer IS the key that belongs on that computer and is the one that should be used during install. during boot up on this PC press f12 (there should be a prompt to press fsomething to get into the boot options...) see if there's a recovery option in that list of options. this is typical of a dell system that doesn't ship with disks, they build in a recovery partition that can be used to do a destructive restore (format/reinstall) to put it back to factory defaults.
On the other PC (also a DELL, I'll call DELL-1) there is not an MS sticker. On Dell-1 prior to HD reformat - Belarc Advisor listed a license (no "OEM" within it), thus I believe this was a Retail version..
However, after the HD reformat I used the only XP CD available (a DELL CD - both PC's are DELL) that gave it the license w/"OEM" contained within it. This I discovered later and it is that "OEM" license I want to change to the Retail? license (listed by Belarc Advisor).
the lack of COA sticker may suggest that this is the PC that that disk belongs to, but maybe not...a lot of times when they send a recovery disk, they don't bother to put the COA since the disk won't ask for it anyway.