I searched the Steam forum as well as this one and didn't find the exact answer I was looking for so perhaps someone can help with this:

The plugin manager displays 9 plugin categories in the left pane. The registered plugins pane displays <<No entries>> regardless of the directories I set under VST configuration. The plugin menu layout is always empty unless I specifically choose the "Music Creator 6 Touch" entry from the drop down list at which point the menu that I would expect to see is shown but there are still no registered plugins listed in the middle pane and when right-clicking in the FX box of a project track none of the menu entries are visible in the right-click menu. 

As an example of the above behavior:
 
After starting a new blank project, I insert an audio track.

When right-clicking in the FX box for the audio track there is no option to select "Guitar AMP Simulator/TH2 Creator" but if I click "load an fx chain preset" and double click one of those presets then TH2 starts up and I can tweak it from there. I can't imagine that this is the desired method for working with the system though.

I've tried executing CWMC.exe as administrator and after this certain VST's elsewhere on my system do get loaded into the FX menu but if I execute CWMC.exe as a standard user no VST's get loaded, and in both cases the default VST's that come with MC6T never are loaded.

System Specs:

Alienware M17xR3
Windows 7 Ultimate x64
8 GB RAM
Over 600 Gigs free space, recently defragmented

Thanks in advance for any ideas!

I'm having the same problem. It looks like the files are not even downloaded. I have been exploring the folders for them, and I don't even see folders for those VSTs.
 
If you find a solution, please post it. I purchased all of the instruments available, and I'm not able to try out any of them.

I found it in the Cakewalk sound studio.
If you insert a sound studio plugin from the plugin tab, and then double click on the keyboard icon on the left of track, it will pop up a interface with midi keyboard underneath and a selection of instruments by types above. I found my piano and guitar extension DSFs in this plugin.
 
So it's not a VST plugins, but more like modules for sound stuido plugins that you bought.