WMP is being used by another program or user?

I am having some problems with WMP 11. It freezes when I run it. I read of a fix online where I have to rename the folder and some other steps afterwards. But it seems I can't rename the folder because it's being used by another program or person. I don't understand. I tried to do it without any programs running, checked all my task list processes and none of them is for WMP, I have no files running and even in msconfig there doesn't seem to be any program running related to WMP. Also, I am the only user on this computer. Anyone know what's happening and what I should do?