Welcome to the forums,
Run anti-virus software and check your system registry for other maladies.
Run a System File Integrity Check by hitting CTRL-SHIFT-ESC to get into Task Manager, and go to File -> New Task -> Run
or if that doesn't work try Windows Key + R on your Keyboard to get to Run
In the Run box type cmd.exe
sfc /scannow
If Windows finds system integrity violations and can't repair them, your installation is corrupt.
Your hard drive may be failing.
You may be infected with a virus, malware, rootkit, or trojan.
Most of these problems will require a complete re-install, and so you should begin the immediate backup of your files. If you did not create a full system backup, this will require a complete re-install of your entire operating system, all programs, and files. If you hear any strange churning or screeching noise emanating from your system, it is likely a hard drive failure in progress. Most of the time, this will not cause you to lose Explorer (i.e. the Start Menu, etc). Usually this is due to system file corruption or a virus.
