Win XP Admin A/c restore

Hi,

I have a lovely new(ish) Dell Optiplex running Win XP O/S that is on our LAN. I am attempting to scan the machine with a 3rd party Utility, to provide a software audit. Unfortunatley, I am denied access to this PC, as the Administrator account appears to have been hidden (or worse deleted)

Is there a way to restore the Admin a/c in XP – without reinstallling the O/S?

Any thoughts would be greatly received.

Cheers,
Simon