Thanks guys for your help.

Sorry about the long post. Yes, I have Win XP Pro on all machines.

If I rename myscreen.scr (the one in the Windows/system folder) back to myscreen.exe and double-click on it, I get the same Bad Image message as before.

It starts by complaining about avicap.dll, then avifile.dll, then commdlg.dll, then lzexpand.dll, then mmsystem.dll, then msvideo.dll, olecli.dll, then olescr.dll, then shell.dll, then tapi.dll, then ver.dll, before finally running level (all greek to me, I must admit).

Stupid question: to rename the application to myscreen.scr, I just do right click->rename-> and type .scr at the end. That's the correct way, right?

Thanks.