Convert SQL Server Express 2005 .mdf to 2008 .mdf

There are a number of limitations, notably:

• Constrained to a single CPU (in 2012, this limitation has been changed to "The lesser of one socket or four cores", so multi-threading is possible)
• 1GB RAM (Same in 2008/2012)
• 4GB database size (raised to 10GB in SQL 2008 R2 and SQL 2012) per database

http://www.dotnetspider.com/tutorials/SqlServer-Tutorial-158.aspx http://www.microsoft.com/sqlserver/2008/en/us/editions.aspx

With regards to the number of databases, this MSDN article says there's no limit:

The 4 GB database size limit applies only to data files and not to log files. However, there are no limits to the number of databases that can be attached to the server.

However, as mentioned in the comments and above, the database size limit was raised to 10GB in 2008 R2 and 2012. Also, this 10GB limit only applies to relational data, and Filestream data does not count towards this limit (http://msdn.microsoft.com/en-us/library/bb895334.aspx).

You are right that the SQL 2008 Express took the 'SQLEXPRESS' instance name. The 2005 toolset cannot connect to 2008. You need to find out the isntance name under which the 2005 VS installed it's Express. Easiest way is to start the Service Manager (run services.msc)and see the instance name there.