a server of our customer has an adhoc ERP system (managed by another company) with database SQL Server 2005 Express and ArcServe (software for backup).
In the database SQL Server 2005 Express there are a pair of databases for the ERP and more than 20 db concerning the software of backup (CA ArcServe).
The customer and ERP company asked us to migrate the 2 db of ERP to version SQL 2008 Express R2.
I ask you if it was possible, on this server Windows 2003 R2, to create a new istance of SQL 2008 Express R2 maintaning actual istances of SQL 2005 Express used until now to avoid configurations problems of backup
software or if there are problems about this strategy.