If you didn't accidentally delete the file and it's sitting in your trash bin, a virus, malware, or some other program may have removed it.

If you find it in your trash bin, restore it. If you haven't scanned your system for malware or viruses, do so.

Make sure your OS has its updates,

Run Windows File Checker using a command prompt as follows:

Open Command Prompt - Start, type run, enter, cmd, enter

Type sfc /scannow enter

Note: In some situations, especially in Windows XP and Windows 2000, you may also need access to your original Windows installation CD or DVD.

Restart your computer after process has finished (5-10 min)

Repeat whatever process caused your original problem to see if sfc /scannow corrected the issue.