only .sh extension I know of is a shell script that would run in the bourne shell (sh).
Never heard of a compression format with that name. Care to tell more, and explain what you've tried ?
BTW: try cat <file> and what does it show ? if it is all just text it is just a script, else it is something else. If it is a script, a simple execution of the script will work wonders.
Let me know and maybe I can help.. because I have no clue atm..
Met