I saw that there was a new update for Studio Instruments as part of the Foxboro release, so I manually downloaded all the update exe's and installed each one.  In a previous install, I learned that StI defaults to C.  I moved it to G:\ and edited the registry to tell sonar that StI was on G.  Everybody was happy.  However, when I installed the manually downloaded StI included with the Foxboro release and ran the exe, it put it on C:\ and hacked the registry.  I had to go back in, move the new files to G:\  and re-edit the registry.  Please fix this before the next StI update.

Hmm, I'm also downloading the installers manually, but rather than running them myself, I just put them in the CW Command Center folder and let the Command Center recognize and run them.   AFAICT, they are installing in my designated (non C: drive)  locations. 

Install it to the C drive you will be fine ;) (Not really)