I've knocked together this short script that I run from Master. Forgive any scripting stupidity - I'm not a DBA - but I think you get the general approach. It assumes you have some idea where the .mdf files are. I'm sure someone could improve on it but it does what I need at the moment.

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if exists (select name from sysobjects where name ='temp_mdf_files') drop table temp_mdf_files

if exists (select name from sysobjects where name ='temp_mdf_dbnames') drop table temp_mdf_dbnames

create table temp_mdf_files (

full_filename varchar(200))

create table temp_mdf_dbnames (

pos_dbname varchar(200))

insert temp_mdf_files

exec xp_cmdshell 'dir e:\*.mdf /s/b'

inserttemp_mdf_dbnames

select reverse(

substring( reverse(

substring(full_filename,1,datalength(full_filename)-4)) ,1,patindex('%\%', reverse(full_filename))-5)

)

from temp_mdf_files

order by 1

select * from temp_mdf_dbnames

where pos_dbname not in (select name from sysdatabases)

drop table temp_mdf_files

drop table temp_mdf_dbnames