Can I switch from MSDE to SQL Server 2005?
Yes. If you are experiencing problems with the limitations of managing your database on MSDE, you should upgrade to SQL Server 2005.
Please refer to the following KB article: Upgrading from MSDE to SQL Server 2005/2008
For reference, Microsoft also has an excellent article describing how to do it: http://www.microsoft.com/technet/prodtechnol/sql/2005/msde2sqlexpress.mspx