How do I overcome this issue:

How do I overcome this issue? Attempting to open iTunes results in a pop up window with this text: "The folder "iTunes" is on a locked disk or you do not have write permissions for this folder". Uninstall and reinstall of iTunes did not correct. No external hard drive or Apple devices are connected to my laptop PC loaded with Windows 7. iTunes was working fine a few weeks ago when I used this laptop PC to access iTunes. What gives? I changed Windows 7 "permissions" to allow 'everyone' complete acess to the PC's folders and contents. Fresh out of ideas.