Sinsull
The best thing you could do is to go into My Computer, select C drive, select the program that he installed and if there is a remove program, remove it or if not, delete the program entirely. The same thing happened here at work in a similar situation and we had to get the IT group to install it and make some changes so everything would work.
I would suggest you delete, get the computer operating and before you install again, use the customer contact and have them walk you through the re-installation.
I hope this helps
Sailor DAn