Two Oracle Instances

Hi,

We had a SAP Netweaver engine (ABAP stack) installed with Oracle 9i in a server. We wanted to install XI instance in the same machine. So we installed the XI instance with a new Oracle 10g database. Now, we are not able to start the old Oracle server. However we are able to start and stop the new Oracle database.

Can multiple Oracle instances can be installed in the same machine?

Regards,

Venkat