And does everything work fine after that? Is W7 fully updated? Have you scanned for malware?
If everything works fine after the error, the system is clean and fully updated, then my "guess" is somehow, you got an entry in your Startup folder or stuck in the registry with a "run" command for a file called "PROGRAM" - with no .3 (dot-three) extension. That is, it is just "program", not "program.txt" or "program.jpg", for example - so Windows does not have a "file association" for filenames with no .3 extensions.
You might try looking in your Start Menu > Startup folder and make sure you understand everything there, if anything. Those are just shortcuts so anything can be deleted with no harm.
If "program" is not listed there, then I recommend running File Association Fixer
(ignore the unavoidable advertisement link to "Click here to fix Windows errors and optimize system performance