Drop offline tablespace

 Hi, hope i dont sound too paranoid but...I am administering a db version 10.2.0.4 on Windows Server 2003 and have a tablespace offline which has only one dbf. This is showing in OEM as size 0.00 and 0.00 used.  I want to drop the tablespace and the datafile.

Currently Rman backups are failing with "RMAN-00571:could not read file header for datafile 7 error reason 4", and datafile 7 is the one offline:

The query:

SELECT FILE#, STATUS, ERROR, RECOVER, TABLESPACE_NAME, NAME
FROM   V$DATAFILE_HEADER
WHERE  RECOVER = 'YES'
OR     (RECOVER IS NULL AND ERROR IS NOT NULL);

Returns:

"FILE#","STATUS","ERROR",                    "RECOVER","TABLESPACE_NAME","NAME"