Okay, it happens.  Eventually you need to rebuild... reinstall the operating system and then reinstall Sonar.  In my case I have Sonar Producer versions right through to Sonar Platinum.  So the question arises, how to do this?
 
I don't have the answers so I'm asking to the Forum.  Questions I'd like to resolve are:

• Do you need to start from Producer X1?  If so why or why not.
• If you install a 'later version' first... is it safe/advisable to reinstall the earlier version afterwards?
• With the new Command Centre and the monthly version updates... How do you proceed?  Do you save those versions and install them successively from a backed up version of the install (it appears you'd have to do it outside Command Centre).

I've sent a request to support but of course input from users who may have done this already is always going to be valuable.
My apologies If this thread has already been discussed.  I did a search but didn't come up with anything.

You may need to install older versions if they contain plugins etc that you want to continue using, you may also be able to achieve that for some by doing a custom install and selecting only those items
 
I believe it is advised to install the previous versions first for various reasons, like a newer version of something being overwritten by an older one perhaps.
 
With the command center -  all updates are accumulative, so there is no need to install them consecutively I believe, there may be some things that were released for a certain month, bonus/special stuff which will/may be required to install separately.

Problem there is... how to quickly establish which build/version came with which particular bonus add-in.  Otherwise you end up with that scenario of having to reinstall an earlier version over a later version.  Which may or may not be safe.

Here is a list of plug-ins by SONAR version http://forum.cakewalk.com/FindPost/3217211 going back to SONAR 8. The order of installation should not matter. That said, I prefer when starting fresh to run advanced installs of older version of SONAR in order. The only plug-in which requires a minimal install of SONAR is V-Vocal. All the other plug-ins can be selected using the custom pick list provided by the advanced install or each version of SONAR.
 
Also the "Loops and One Shots" bundled with X2 and X3 Producer are the content from the Beatscape synth. The synth was dropped from X2.

Thanks scook and Mr Cranium.  I'll check out the link.

Windows 10 and a new SSD make this likely for me soon. I am about to start writing down the order I want to do things in and any things to be concerned about or tips. I believe it will help me through this. If I do a good job the hard part will be done when the plan is done and the actual install will be the easy part. I hope.

Okay, so just ignoring X versions for a minute.  What about if I install the latest Platinum Update and then install the Platinum Core Plugins one by one from the start.  Does that sound like a reasonable plan?

All Platinum installers are cumulative. Install the most recent version of each and you will have a current version of Platinum. This is what the Command Center will do automatically. By "Platinum Core" if you mean the "Platinum Core Plugins" installers shown along with the SONAR Platinum installers in your account you only need to install the most recent one. If you mean the other installers below Platinum such as Classic Creative FX Suite, Engineering FX Suite, etc., yes install the most recent version of each.

All right, I think I understand that.  And yes, I meant the core plugins listed below the version update.
So what I'm thinking is: An install of Producer X2 and then the Platinum install.  The way I'm seeing it is that I would lose Beatscape and the Blue Verb Suite.  But it would keep the re-installation fairly simple.
 
The other programs like AD2; the AAS suite and Melodyne I own separately and can install separately.
 
Does anyone have any comments on the Blue Verb Suite?  Sorry, meant Nomad Factory Suite.

malcolmd
Does anyone have any comments on the Blue Verb Suite?

I think you are referring to the Blue Tubes plug-ins. They are bundled with SONAR Platinum.