Hello,
I had an issue with my Xp Pro as in it was running real slow & strange. The start up & close down screens were also different amongst other anomalies. Originally I had SP1 installed off a copy of a windows CD with a vaild COA & then downloaded SP2 off MS web site.
Anyway system got bogged down & when I went to reinstal O/S MS advised COA was no longer a valid unit. Bought a Dell reinstal CD ( new & sealed) with a valid COA which installed OK but left me with a SORT of duplicate instal. IE  In Explorer it would show the user twice in the root directory with the same folders eg: in Docs & Settings it shows Administrator & Administrator xxxx;User 1& User 1 xxxx & so on.
When reinstalling I chose the option to PERFORM a clean instal then did it again with the repair option but still gave the same results.  
I am now of the opinion I need a complete 'from scratch' instal, so I guess my question is can I do this with the Dell CD or do I need to purchase a new copy. I have been checking E Bay for clues on what is available & there appears to be different versions- upgrade, 'New in a box', a Dell version like I have or a hologram Cd with just a booklet.
My unit is 1.27ghz Athlon XP 512RAM 40gbHDD  & Gigabyte7VM400M-RZ
If anyone has any clues or suggestions they will be welcome. Pls advise if further info needed.I Depends of the Dell CD you have

If you have one That is just a windows CD re-branded you can, This is likely the CASE

but if its a Dell Recovery CD , you should also be able to , and now you have 2 licences : After installing 3 time MS make it harder for you but if you ring the phone number on the Activate Screen they will give you a good Activation CodeThe CD is green with 'Operating System already installed on your system' Reinstallation CDDo you have the option to format the drive prior to installation? Some makers call this a "Destructive Install".No, I don't think so. Does the limit of 3 instals count from actual instals or activations?