It sounds as if the desktop shortcut to the database is corrupt and pointing to the wrong location.
You can check where Access should, by default, be saving databases. Open Access 2007, Click on the MS button top left, Choose Access Options(bottom right in that window) and on the popular tab it will tell you where it should be saving the database.
If you open that location you should find your databases.
Right click on your desktop shortcut and choose properties and check the target location.