Getting errors when installing second instance on Oracle 10g on the database machine (server)?

The scenario is like this; we have a database server with Oracle 10g installed, with an instance already in use, lets call this Instance1 (with the same SID). Now, we want to have a second instance on the same server, with SID i.e. Instance2. I try to use the DCA (Datab开发者_如何学JAVAase Configuration Assistant), but keeps getting errors at the end of the creation (normally around 85%).

Error message goes like this:

Enterprise manager configruration failed due to the followin error - 
Error starting Database Control Refer to the log file at C:\oracle\product\10.2.0\db-1\cftoollogs\dbca\Instance2\emConfig.log for more details. You can retry configuring this database with Enterprise Manager later my manually running C:\oracle\product\10.2.0\db_1\bin\emca script

I'm getting the feeling that I need to do this commandline, and maybe change some config files. Could anyone please give med some pointers, or any good guide I can follow? Thanks in advance.