So I still use 8.5 for a lot of projects, though I have updated through to Platinum. But recently, I noticed that I don't have the same basic things I used to in 8.5... Lexicon Reverb, the basic set of CW effects. Sonitus is still there, but not those other ones. And V-Vocal still shows up as an option, but is grayed out for use. 

If I open up old projects that used Lexicon or the other CW effects, they are still there and sound fine and can be exported and such. But any idea about why they are no longer showing up in 8.5 for me? Did one of the later installs (X3, Plat, etc.) make those things go away? I'm running 8.5 (64) on a Win7 machine.

I'm making the same transition from 8.5 to Platinum.  I was able to get V-Vocal working because I haven't learned how to use Melodyne yet. Check out all of the paths that you use for plugins in 8.5 (using the plugin manager tool) and then put all of those paths in the plugin manager in Platinum. That should do it as I have all of my old plugins available in Platinum now.

I want those things to work in 8.5, though, not Platinum.

They should still be there. AFAIK, new SONAR installs do not delete anything. First, check to see if Pantheon and V-Vocal are still physically there. I don't have 8.5 anymore, but IIRC V-Vocal was under Shared DXi. Pantheon may have been in a subdirectory below vstplugins, but I don't recall.

Peripheral question... how do I uninstall Platinum? I don't even see it in the list of programs in Control Panel.

I wouldn't do it. You could accidentally get rid of something you want to keep. Even if you wanted to revert to 8.5 for good, many of the newer plugins that came with Platinum can be used in 8.5.

Anything installed with the Command Center is maintained in the Command Center. Right-click an item in the Command Center to see the uninstall option on the context menu.

Ah, command center. Ok, right.

Pantheon should be under Program Files/Cakewalk/Shared Plugins.
 
V-Vocal and Pantheon are DX plugins. So you don't need to set the paths in VST Scan.

bitflipper
I wouldn't do it. You could accidentally get rid of something you want to keep. Even if you wanted to revert to 8.5 for good, many of the newer plugins that came with Platinum can be used in 8.5.

But if it's holding up V-Vocal and other things from being used in 8.5, I'd probably rather not have it. I use that more than any of whatever came with Plat. Better case would be to figure out how to get that stuff working in 8.5 again, without removing Plat. But it seems as though that is the culprit, somehow, right?