COMB2, as well as the other Garritan products aside from Steinway, get played through the new ARIA player standalone. I believe ARIA gets installed as part of the standard installation. If it was de-selected during the install, you can download it here:
ARIA was developed by Plogue in collaboration with Garritan.
On Windows systems, ARIA is typically installed to the folder: C:\Program Files\Garritan\ARIA Player (or ...\ARIA Player x64) There may also be files located in: C:\Program Files\Plogue\Aria
The above folders can be checked to see whether or not ARIA was installed.
I hope that this helps.