Reinstall another CLEAN (and free of viruses, and, of course, your PC) version of Clipper. Is "strange" your message: c:\clipper.exe. Clipper.exe would be under the directory c:\clipper5\bin\. NOT c:\.
Review your install. Also give us a hint of in which plattform yow are working (Win 95, 98, 2000, etc.)
Regards. Also take a look at the documentation about the environment Clipper needs to work.