If you're running a 64 bit version of windows, when you display the speech control panel, the panel will display only 64 bit voices installed on your system. To date, the only 64 bit voice we've run across is Microsoft Anna. In order to display 32 bit voices, you need to run the 32 bit version of the speech control panel, here is how to do it.
If you're running Windows Vista, display the Control Panel from the Start Button, and click "Classic View" on the left pane. Click "View 32-bit Control Panel Items", and then click "Text-To-Speech". This should run the 32 bit speech control panel and display your 32 bit voices.
I don't know of an equivalent in Windows 7 64bit, but you can access the 32 bit speech control panel by opening windows explorer, and pasting the following text into the address field at the top:
%windir%\SysWOW64\speech\SpeechUX\sapi.cpl
Press the enter key to display the control panel.
Related, see viewtopic.php?f=11&t=5569
