Windows XP Pro – Can’t run EXE’s

I have 2 clients that for some reason can’t run any EXE program. Keeps saying it can’t find files etc. One person gave me a file on disk that is called xp_fix_exe. It is a registry file fixer. Once the you double click on it it repairs the area needed in the registry. Now you can go back and run EXE’s. BUT, if you logout and log back in, you’ve lost EXE’s again. You can run the fix file and your back in business. I have everything to fix this. Please any ideas. Is it Spy/adware virus what !!!
Thanks Noel