MS Office Accounting 2008

In MS Office Accounting, when attempting to enter a transaction, I received an error indicating that there was 'insufficient disk space in filename "Primary", and suggesteted that I set 'Autogrowth'. I attempted to upgrade to 2009, and got the same error. Can anyone give me a clue as to where and how I can overcome this file size limitation? There are many gb of space available on the drive, so it is not a physical space problem.
Thanks