XP Pro reinstal problems

[barndoor]

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.

[panboy]

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 Code

[barndoor]

The CD is green with 'Operating System already installed on your system' Reinstallation CD

[GX1_Man]

Do you have the option to format the drive prior to installation? Some makers call this a "Destructive Install".

[barndoor]

No, I don't think so. Does the limit of 3 instals count from actual instals or activations?