I had the same issue that you are currently experiencing. This is due to the "OfflineActivation" folder which cannot be deleted or altered in any way. To solve your problem, I would run Windows in Safe Mode, click here, and that should clear the problem. You may also want to check out this link, assuming you have Windows 7, although it is pretty much the same for other versions of OS.
edit: as JAM-Justin35 has pointed out, if the above does not solve your problem, please create a new thread after reading the stickies.