Two possible cures, certainly ones which I would try before getting too dramatic about the problem and reaching for the bigger hammer. It sounds like you have corrupted OS file(s). Which one you try first is up to you but I think the first one below is easier.
If this problem only started relatively recently, say within the last three or four weeks, then do a system restore to a time before the problem started. Click 'Start - Control panel - Recovery - Open system restore'. This will bring up the restore screen which will list only the most recent one or two restore points. If these pre-date your problem pick the appropriate one, if not click the button 'More restore points' and then select one that pre-dates your problem. Click 'Start restore' (or words to that effect) and accept the warnings that this is an irreversible process, and sit back and wait for it to finish. This process should only take 5 - 10 minutes, then, if it doesn't re-boot itself, re-boot, then check that the problem has disappeared. It may now be necessary to re-install any updates since the restore date. Do these one at a time as it may be one of these that caused the problem in the first place !
The other method is to run a program called SFC /scannow. This restores corrupted Windows files. To do this you need to open the command line. Click on 'Start' then type 'cmd' (note, all typing commands WITHOUT the quotes) into the search box. This will produce a list with at the very top 'command.exe'. RIGHT click on this and, from the pop-up menu that appears, select 'Run as Administrator'. This will produce a small black window with white text which will end with a prompt. Just type 'sfc /scannow' at the prompt - case doesn't matter but note there is a space between 'sfc' and '/scannow' - then press 'Enter'. The computer will now start to scan and repair system files.
This process can take quite a long time, 40 minutes to an hour is not unusual so leave the computer running and go and do something productive. When you are certain that the scan has finished, re-boot and you should be good to go.
If neither of these methods solve the problem, post back.
Edited by Chris Cosgrove, 08 November 2014 - 06:44 PM.