Try this:
Go to Tools menu and choose Folder Options.
Next choose the View tab.
Select Show hidden files and folders.
Next uncheck the box next to Hide extensions for known file types.
Then uncheck the box next to Hide protected operating system files
(Recommended).
Now go in to the C:\WINDOWS\system32 folder and the look for cmd (or
regedit).
See if there are two files with same name, but with different extensions.
Delete the file with the .com extension, also note they are 0 KB in
size.