>How can I suppress the message "file not found" in FP for dos 2.6 when I try to delete temporary files and backup files during runtime? I'm using this command :
> RUN del *.tmp
> RUN del *.bak
>inside my prg.

Alter the default .PIF settings for the command processor, or don't shell out to DOS. You'd have to make changes to the basic MSDOS command processor PIF settings; the exact setting mechanism vary from OS versions, and under pure DOS, are not directly controllable.