A few questions:
-Did you turn off and restart the computer? (sometimes doing the obvious can work)
-What version of Windows are you running?
-Do you have up-to-date antivirus? (a virus can cause this or other problems)
-Can you start the program by entering taskmgr.exe at the run command? (let’s see if you can run the program a different way)
-How much memory does the computer have? (maybe the computer is too “overwhelmed” to start another program)
-How old is the computer?
I suggest you Google “cant start task manager” (sans quotes) for suggestions and ideas.
You may simply need to change some settings. Some sites give step-by-step instructions for changing settings, with pictures.