database to use for Automated Teller Machine
For projects using Visual Studio, I'd almost invariably recommend using SQL Server Express.  The product is free to use, as long as you can live with the limitations: Microsoft SQL Server Express supports 1 physical processor, 1 GB memory, and 10 GB relational storage.  I'd expect for an ATM project you won't be locally storing a lot of data, so that shouldn't be a concern.