There are three keys in the registry for Session Drummer 3 in
HKEY_LOCAL_MACHINE\SOFTWARE\Cakewalk Music Software\SessionDrummer3 Contents Folder - directory containing the Contents folder (I have moved mine, I believe it defaults to "C:\Program Files\Cakewalk\Vstplugins\Session Drummer 3" Note: this is the directory above Contents)
Resources Folder - the Resources folder (default = "C:\Program Files\Cakewalk\Vstplugins\Session Drummer 3\Resources")
Documentation Folder - the Documentation folder ("C:\Program Files\Cakewalk\Vstplugins\Session Drummer 3\Documentation")