Is this Windows 7 SP1 (Service Pack 1) and are Microsoft Updates current? You can tell if it's SP1 by right-clicking 'Computer' on your desktop or in the Start Menu and then selecting Properties. Also can you open Internet Explorer (whether or not it's your default browser) and go to Help/About and tell me the version please? If it isn't IE9 I suggest it should be at your earliest convenience.
This could be caused by malware or simply corruption which can be caused by a number of things but usually by indiscriminate use of registry cleaners and/or optimizers. If that's the case see if they have restore button.
Talking about restore, System Restore would be your easiest way out of this situation. If you can't initiate it in regular more you should be able to in Safe Mode, reached by tapping F8 repeatedly while booting up and it's usually the first item on the menu that appears.
System Restore is located in the Start/All Programs menu under Accessories > System Tools or simply type rstrui in the Search box immediately above your Start Button and when it appears in the window above, click it.
Try to go back to before all this started. If successful temporarily disable System Restore by turning it off and then back on again to get rid of the bad restore point.
An excellent forum for Windows 7 help is located HERE.