OK, I re-read your post and see that you want a list of paths.
You have it right; minimum 3 drives.
C: OS and all "programs" (except Rapture).
dlls go C:Program Files\Cakewalk\Vstplugins\vsti sub folder
I assign sub-folders for each VST and VSTi; these are the dlls. your circus, your monkey.
Audio Drive; mine is "A" since Win 7 will "let" you name an HDD "A"
I have a sub folder called CWP. That way I can backup all projects to an external drive with one move of the mouse.
Sample Drive, "S" works for samples, or V for VSTi, or L for Library; call it what you like.
I made a folder called "VSTi"
I have sub folders for "Cakewalk" "IK" "EZD" etc.
The only one I had "issues" with is Rapture.
It does not let you specify where samples will go (if my notes are right).
Consequently I installed Rapture (the program and samples) to the sample drive.
DimPro, Zeta, Session Drummer, IIRC, all let me specify where the samples should go.
I had no issues with SampleTank3 putting all the "content" on the sample drive.
You've got to pay close attention, as you're finding out.
Most installers will let you choose, but you've got to be "on your toes".
SampleTank2 works in X3?
All the "old" IK synths quit on me when I installed X2.
Have fun
Tom