How to install 2 Catia V5 versions on one machine

As a Solidworks application engineer, I don't have any knowledge of Catia. I hope you can help me.

One of our customers has a Catia V5 license. They are running a newer version then a customer of theirs. Customer asked us if and how they can install 2 versions on the same machine.

I believe they are running R26 and want to install R25 beside it.

Any tips and tricks on how to do this (What are the pitfalls, what to take into consideration, etc.)?

Thanks,

Bob