>I still have Clipper (DOS) app, which I run from the command windows.
I don't know what happened, when I run the app today, it didn't give any respond (go back to C:\). then I tried all the DOS app I know, such as old Norton Utility, PKzip, etc, same thing, no respond and nothing happened.


I imagine you're running this application from Windows and inside a DOS window.
What version of WIndows is running?
What did this Clipper application do when it worked properly?