Steps to drop your 10g database:
bash$sqlplus "/ as sysdba"
SQL*Plus: Release 10.2.0.3.0 - Production on Tue Jun 24 17:40:08 2008
Copyright (c) 1982, 2006, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup restrict mount;
ORACLE instance started.
Total System Global Area 838860800 bytes
Fixed Size 2076464 bytes
Variable Size 805306576 bytes
Database Buffers 25165824 bytes
Redo Buffers 6311936 bytes
Database mounted.
SQL> drop database;
Database dropped.
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
All files that relate with the database control-file will be deleted as well. But all other file, *dump, password file, pfile still intact. If you wish to delete completely, use $ORACLE_HOME/bin/dbca