I am thinking of upgrading to X2 but i currently use 8.5 Producer. Until I fully grasp the X2 can i still have 8.5 to use or once i install X2 does that upgrade everything to it? 

Yes, you can have as many versions of SONAR both 32 and 64bit as you own. With the exception of shared utilities and plug-ins, each installs in a separate directory.

thank you! and great to know. 

I would add, it is a good idea to keep the prior versions installed as long as there is disk space for them. Each version typically takes up less than 200MB. The bulk of disk used by SONAR are content such as loops and plug-in sample libraries. Content can be shared by all versions of SONAR. Having older versions installed can:

• Aid with transitioning, as you want to do
• Add plug-ins that are no longer included
• Assist with problem solving such as open older projects that have problems with newer versions

Just be sure to keep the 8.5 version of projects separate if you work on them in X1 or 2.  If you change effects or use X stuff you might have problems opening them in 8.5.

That is true. It is a good idea to work on a copy of the original project whenever opening an older project in a newer version of SONAR. Each version does introduce some changes that might not be compatible with a previous release.

+1 to what AT said. I have two main Sonar files, One says "Sonar 32" and the other "Sonar 64"
An interesting thing too, I still have the demo of X1 installed but of course cannot open it, but I think some of the plug ins will work in 8.5 now?? not sure because I haven't used them, but I'm sure my plug in list grew the day I installed  the X1 demo. 

Yes and some of the shared items get updated with the demos too. Those updates do not expire or it would break your existing installation.

Begin humor.
 
I have every version since 8.0(lastest update) to X2a. They all get along for the most part but sometimes they get rowdy and I have to lay down the law. ;-)
 
End humor.

I may be checking back in my most recent 8.5 for a few things.  I've got alot of interest in the matrix at the moment.  Seeing if I have the same experience on each version.