Running multiple Oracle homes on Windows

I need to upgrade some existing instances from 11.1.0.7 to 11.2.0.3. I only have one sever to work with so my high level plan is as follows:

1. Install the 11.2.0.3 software.
2. Clone one of the existing 11.1.0.7 instances for testing by editing the output of "backup control file to trace" and using ordim to create a new Windows service.
3. Upgrade the test instance.
4. After appropriate testing, upgrade the production instances.

This plan depends on my being able to control which ORACLE_HOME each instance uses. On my UNIX-based servers, /etc/oratab provides this function. How do I do this on Windows?

Thanks,
Peter Schauss

--
http://www.freelists.org/webpage/oracle-l