Hey Auger,
Administrator Access Rights are required in order to install anything on XP. I think your best bet would be to take the computer back to the person/company that did the upgrade so that they can sort it out for you. Doing so by yourself may void any warranties or guarantees that you have with that person/company.
What is an sp pack?
I think what Ozzy means is Service Pack. They're upgrades to the Operating System. At present there are two Service Packs available for XP, namely, SP1 and SP2. SP2 was released a few weeks ago. If you right click on the My Computer icon and go into Properties, it should tell you if you have any SP's installed.
Regards,
Stratobat