Hi Sonia,
Could you check the presence of temp file under dba_data_files ?
If the files are present as data file & not temp files, you may need to drop them as well.
Also as per oracle docs, if the data file is offline it cannot be dropped.
http://docs.oracle.com/cd/B19306_01/server.102/b14231/dfiles.htm#i1006556
you may try this command to drop the offline datafile
ALTER DATABASE "DATAFILE '' OFFLINE DROP;
Hope this helps.
Regards,
Deepak Kori