All the prompts are listed in PROMPT.INI files found in each directory under \commserver\localization\prompts\ENU\...
The directories are broken into components - the one you want is in PHGreeting (the call handler greeting conversation) - you should find what you're looking for there.
For details on this specific prompt, see this thread:
http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&type=bookmarks&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40.ee83e4c/0#selected_message
Also, keep in mind that TAC doesn't support folks fiddling with their prompts - these changes will be wiped out on your next upgrade to make a note of what you do.