Actually, if you use a client (YahELite or Y!mLite), you *should* also copy over to the system32 folder and register it with regsvr32, since a couple clients use system32 for the yacscom.dll file for voice.
Download and run
this file and it'll install the TSP codec, and install/register the hacked yacscom.dll to the system32 folder for all clients to use.
I'll be updating my Vista voice tutorial in a bit to reflect this.
