The answers depend on the manufacturer and model...and your wishes
Restore disks and partitions...are routinely employed by system manufacturers as the means for returning the system to factory conditions. The procedures for using such are usually available at the website of the system manufacturer.
In the event that the system is custom/self-built and the user actually has a Genuine XP CD...simplest thing to do is delete the partition, then install anew, using the XP CD.
As for the system admin account...any other admin account created can replace that, I believe. If I wanted to such, I would simply create a new user account (titled NEW) then delete previous user account (Louis).http://www.microsoft.com/windowsxp/using/s...p/accounts.mspx