Can anyone tell me how I can remove all references to previous users on a PC?

One of our users is having a spare PC. I have created a new account and then deleted the previous users account and files but everything is still registered to the old user, even at the DOS promt.

Is it a case of altering every registry entry that mentions the previous user or is there a simple command that will do this for me?

No need to worry, I found it!

Run the Registry Editor (REGEDIT.EXE).
Open HKEY_LOCAL_MACHINE\ SOFTWARE\ Microsoft\ Windows NT\ CurrentVersion.
To change the values of the RegisteredOrganization, RegisteredOwner, or ProductId, simply double-click on them.