We have put the CRD database on a full edition of SQL Server 2008, so we can back it up using SQL-Agent.
We use this isnstance for a number of other tasks, but I'm not sure if you coul djustify the license just for CRD? If using SQL 2008 Express, how are you going to run database level backups?

If it is just the CRD database that you are looking to backup, then we use the scheduled backup ability within CRD to do this.

If anything should go wrong we can just restore the backup via the 'restore system' in CRD.