All projects and archive data are stored in a SQL 2000/2005 database. The database name is MSEA_Graphics by default. If you are using SQL Express as your database (as opposed to SQL Server), then you must make sure keep your database size less that 10Gb in size.
You can see the size of all SQL databases in the HELP-About menu. Also, the schema version of the MSEA_Graphic database is show here.