This is the Vista forum, but I'm assuming you are wanting to restore XP. The manual that came with your PC will tell you how, or you can search Dell Tech Support.

http://www.michaelstevenstech.com/cleanxpinstall.html
http://www.winsupersite.com/showcase/windowsxp_sg_clean.asp
http://www.djdenham.com/Install%20Procedures.htm#Install

Driver Installation:
http://support.dell.com/support/topics/global.aspx/support/dsn/en/document?c=us&cs=19&docid=1A0C0937D62A8739E0401E0A55174744&journalid=4F1F82483DC811DBAE564F9328EE04A4&l=en&s=gen