I have previously installed SQL Express and converted all instances other than SIMS over to this (ie. Backup Exec, Sophos, WSUS 3).
When running the migration tool i get to the "Select and connect to your SQL2005/SQL Express Database Server" screen but from the drop down box this only gives me the option to choose one of the Three instances that already exist ie. SERVER01\MICROSOFT##SSEE, SERVER01\BKUPEXEC and SERVER01\SOPHOS
Surely i don't select one of these as they are already being used!! A little help would be magic 8O