Error number 3197 : The Microsoft Jet database engine stopped the process because you and another user are attempting to change the same data at the same time.

My MS Access File has been corrupted, how to repair this file

This article gives a full break down of your problem.

The article Ben linked to shows you how to attempt a compact and repair. Hopefully that will work. If it doesn't work let us know there might be other things you can try.

Once you have gotten the database fixed, you should take steps to prevent this happening again. If this database is a multi-user app it NEEDS to be split. Splitting involve taking all the tables and putting them into a back end file. Access includes a wizard (under Tools>Database) to do this for you. The wizard creates the new file, moves all the tables into it and creates links in the front end to those tables. You then put a copy of the front end on each user's PC.

You also need to create a backup policy so you have a backup copy of both the back end and the front end at least daily.