mag@itloaner1_local > select tablespace_name from dba_tablespaces;

TABLESPACE_NAME
------------------------------
SYSTEM
RBS
USERS
TEMP
TOOLS
INDX
OEM

7 rows selected.

--
-- you cannot just drop the tablespace if you have some data in it
--

mag@itloaner1_local > drop tablespace tools;
drop tablespace tools
*
ERROR at line 1:
ORA-01549: tablespace not empty, use INCLUDING CONTENTS option

--
-- so use including contents
--

mag@itloaner1_local > drop tablespace tools including contents;

Tablespace dropped.

mag@itloaner1_local > select tablespace_name from dba_tablespaces;

TABLESPACE_NAME
------------------------------
SYSTEM
RBS
USERS
TEMP
INDX
OEM

6 rows selected.
--
-- But this wont delete the datafile physically (8i). 
-- in 9i, you can add this clause so that, the concerned datafiles are also dropped.

mag@itloaner1_local > DROP TABLESPACE tool INCLUDING CONTENTS AND DATAFILES;