We've had a number of customers ask us for advice on backing up their data recently. Our advice is to keep you spring design database file located on a file server where it can be backed up with your other data. Simply make a copy of the ISTSpringData.mdb file on a network share, and use the IST Config program to use this as the default database file in future.
If you want to copy across your existing database file (to work from going forward), it is located in the application installation folder, which is by default C:\Program Files\ISTSpringDesign (or C:\Program Files (x86)\ISTSpringDesign on 64-bit Windows). One thing to be careful of here is that usually your springs are saved in a copy of the file - you need to click on "Compatibility files" to see the version to put on the network. Otherwise you'll get an empty database!