You'd have to format the hard drive (erase everything) and do a clean install of Windows 7 and ALL of the programs and files currently in the PC Minz
it's doable and you're not idiot....but you need a Win 7 dvd and copies of all of the software currently in the PC....they may have partitioned the hard drive and put some backup or restore files on the laptop to allow you to reinstall everything the store put in...but again, you have to know how to do it and should have someone experienced help you