I downloaded the latest Oracle versions for studying. (I don't have a metalink account because I am actually not working) I want to install Oracle Database 11g + Oracle Developer Suite 10g on the same Windows XP Desktop. I did the following steps : - Install Oracle Database 11g in ORACLE_HOME "C:\oracle\product\11.1.0\db_1". - Create a database DEV - Startup database DEV, listener and configure sqlnet.ora+tnsnames.ora - Connect to the database with sqlplus system@dev => connection succeeded - Install Oracle Developer Suite 10g in ORACLE_HOME "c:\oracle\product\DevSuiteHome_1" and choose Installation Type "Complete (1.13 GB)" When I install Oracle Developer Suite 10g I receive the following error: Oracle Developer Suite 10g (10.1.2.0.2) cannot be installed into existing Oracle9i 188.8.131.52.0 or higher Oracle Home. I don't understand why I receive this error. Oracle Developer Suite creates a separate Oracle Home, so I don't understand why the error says that it tries to install into an existing Oracle Home. What must I do to solve this problem?