We really need more information on which version of Movie Edit Pro and Windows you have, do any error messages popup on start up?.
Please read this post
As a start - with MEP closed down, use Windows Explorer to search for movieedit.ini or videodeluxe.ini ,depending on which version of MEP you have, the files may be hidden so you wil need to turn on 'View hidden files' in Windows Explorer's Folders and search options.
There may be several of the files , the one you want is the largest, delete it and then start MEP.