Re Rapture:
I've had a bit of a play and think I can explain your situation (which ain't too bad, if an issue at all) ...
The Rapture install only asks for 2 locations:
1. An install location
---- for you
E:\Program Files\Cakewalk\Rapture2. A VST install location
---- under which it'll put
\Rapture\rapture.dll (I tested on a 32bit Vista box ;) - I seem to recall my 64bit Win8 install asked whether you want to do an x32 or x64 install as an initial radio button check - hence still only asks for one VST location per install).
You don't get a choice where the Programs Tree goes (EG, MIDI, Programs, Sample Pool, SG). It goes to
C:\ProgramData\Cakewalk\Rapture. (Actually, it probably goes to where the
%ProgramData% environment variable is defined - you can check it via
Run(Win-R)>cmd ; echo %ProgramData% ; exit ).
So your mate has simply chosen to install to your second drive, which is quite a 'normal' thing to do.
Is the speed of the drive noticeable? (I'd have thought 5400 rpm should work OK).
If you really wanted to change it you could do a (backup) uninstall/reinstall.
Take a note of your serial number first (click on the Rapture logo (top right)) - it's needed during installation.
Even if you don't have the install file, you should be able to download it from your Cakewalk Store Account (your serial number will be there too). (It's also retrievable from the registry - I can help, as I'm sure others can).
Or:
Issue 200 of Computer Music magazine (~$5 iStore, Google Newstand, Zinio) has the full version of Rapture.
RE: VSTs
[It appears I still can't post that link].
Yeah - a bit of an issue if things are all over the place.
BUT ... I've read advice NOT to do a full disk VST Scan. (Sonar can get hung/crash at startup).
I had my first play with Plugin Manager tonight. It looks like your organization can be handled with a Layout File (.pgl) - (top right). Sonar Studio has a layout similar to the one you've described for effects (X3 Studio Effects -
C:\Users\<username>\AppData\Roaming\Cakewalk\SONAR X3 Studio\Plug-in Menu Layouts\X3 Studio Effects.pgl). They are also under
C:\ProgramData\Cakewalk\... (search for .pgl).