DOs commands are not working

I feel/know one of my colleague has made some changes/rename with these files to prove his genius!??. When I type these commands,

c:\.>fdisk

‘fdisk’ is not recognized as an internal or external command, operable program
or batch file.

c:\>poledit
Cannot find the file ‘poledit’ (or one of its components). Make sure the path and filename
are correct and that all required libraries are available.
can you help me.