How does one go about using both CS versions for their mod? You see, I'm creating a mod for the Shivering Isles, but at the same time I am going to need to generate .lip files for voice acting. Before I had installed the latest version of CS, but right now I need the old version. I downloaded the installer and tried installing, but it's instead asking me if I want to uninstall the new CS I already have.

So what I'm asking is, how do I install both versions? I've heard others talk about running both construction sets at the same time, so I don't see swapping between both CS versions to mod SI content and generate .lip files as a realistic option here...

Please help, I'm not sure what to do.

Have you seen http://cs.elderscrolls.com/constwiki/index.php/The_Elder_Scrolls_Construction_Set?

You do realize that walkthrough assumes you've already installed both versions?

In any case I believe I've figured it out. No need for this thread anymore.

Perhaps someone else can need a hint, how you can install both versions:

You just have to delete/rename the folder "C:\Program Files (x86)\InstallShield Installation Information\{23D683DD-93C6-48E6-B84E-78B57778F126}".
If you rename/delete this folder, the setup thinks that you don't have installed a CS and allowes you to install the second one without deleting the version, which is allready installed.