You need to move the SQL Server database files by following the proper procedures. You cannot simply cut and paste it between directories, as the SQL Server process is continually accessing (and will have a lock over) the files.
The procedure you can follow to move the database files is detailed in
http://www.cryer.co.uk/brian/sqlserver/howto_movedatabasefile.htm.
Once you have moved and reattached the database, you will then still be able to access that SQL Server database in Management Studio.
-tigermatt