There has been an issue with voices not showing up registered within Windows Vista although the voice has indeed been registered with Cepstral Tools. The solution to this issue is simple, please read below.
When registering a Cepstral voice in Windows Vista the voice has to be registered while running the 'Cepstral Tools' application as an Administrator due too security functions within the operating system.
1. Select the 'Start' menu.
2. Inside the search field type: Cepstral Tools
3. Right-click the Cepstral Tools Icon to open the file options menu.
4. Towards the top of the menu, there should be a function called "Run as an Administrator", select this function.
This will open the Cepstral Tools application with administrative privileges, allowing the license key to be registered and written without any issue.
I hope this helps.