@ahmed: you have never clarified whether users are using the same front end located on the network or they each have their own local copy. If the former, moving the backend to sql will not solve the problem since users sharing the FE will cause corruption in the front end.
If you go the wireless route, use a sql backend for definite (sql server express is free) and each user must have a copy of the FE on their local machine.
If you go the wired route, you can stick with access as a backend but each user must still have a copy of the FE on their local machine.