To move the existing database files?
Run ALTER DATABASE dbname MODIFY FILE (NAME = 'logicalname', FILEPATH = N'new_location')
Take the database offline, move the files, then bring the db back online.
More info here: http://msdn.microsoft.com/en-us/library/ms189133(v=sql.105).aspx
You can change default data & log file locations for new db's in the Server properties screen in SSMS.
Not sure about "won't allow me to attach newer databases." - what's happening when you try?
Thanks
Gaz