You may have a malware infection, as this is one of the features they love to turn off.
Restart your computer in 'Safe Mode with Networking Support'.
(To do this: Power on your computer and start tapping the F8 key at the top of your keyboard rapidly until the Windows Start Menu appears. Then select the Safe Mode with Networking Support menu option and press the Enter key)
Open your web browser and go to www.malwarebytes.org
Download their free malwarebytes program from their main page
Install the program on your computer and run it.
Update the Malwarebytes program and do a full scan.
(You may be asked to restart. Do so, but use F8 key to return to Safe Mode)
Then restart your computer in Normal mode.
Go to www.superantispyware.com and download superantispyware
Install this program and update it.
Click on the Preferences button and then the Repairs tab
Apply these repairs and you should be back to normal
Let us know the results of the scan and whether or not any symptoms persist and we will troubleshoot deeper.