AFAIK there is only oagent.ShowDefaultCharacterProperties that displays this information. Registry does not contain information about characters.
Usually character files are located in the
getenv("WINDIR")+"\msagent\chars\". They have file name as character name and extension .ACS. So you could scan the directory and gather file names.

>Does anyone know how to get a list of microsoft agent characters that are installed on a workstation?
>
>Thanks