Accidently deleted some mathcad program

Hi all, I accidently deleted some mathcad programs.

I recovered mathcad worksheets from some recovery softwares

but when I try to open the recovered mathcad worksheet, I am getting

a dialog  box describing as " The requested file is not a valid Mathcad XML worksheet ".

It means when mathcad worsheets once deleted cannot be opened in mathcad ?

Please someone help me in this issue ?