MS DOS commands not working?

Alright so I am an absolute beginner at this so please keep it simple.
I am trying to open a file on Windows Command Prompt. I am using a software called PLINK (for GWAS) and my code looks like this:

C:\Users\bb17ttg>plink –bfile /raw –hardy –out raw

I have tried everything: writing the entire path of the file; copying the file onto the path; changing the working directory (which I haven’t managed either). I am at a complete loss with this. What am I doing wrong?