Can not delete Program Files folder??

In troubleshooting on another persons computer I uninstalled about 20 games their kid had installed without knowing which ones, if any, were compatable with XP, then went to “Program Files to finish up deleting remanents of what was left, folders that were dedicated to the installed software. I cannont delete one folder. Usually all you have to do is open up the folders and first delete everthing inside and then you can work your way back out, deleting all the way, until at last you can delete the actual folder. This one won’t even let me open it or rename it with another file name or extention, even though just a folder and it’s size is “0 KB.” Trying to delete or rename ends with “Access denyed” HELP! There must be some utility or trick that will kill this little thing???
Thanks!