I went through this same problem when I got my Touch. Then when I dumped the touch and got a Mogul, same thing again. Fortunately I remembered where I had put the files that I had found before
Download the attached file and copy it it your Mogul. Unzip the file on your Mogul's storage card. Then, using a non WM file explorer (I use Resco File Explorer 2007), move the files as follows on your Mogul. You can backup the original files if you prefer, but either way, overwrite when prompted.
voicecmd.exe --> \Program Files\Voice Command\
VoiceCmdRes_PPC.dll --> \Program Files\Voice Command\
VoiceCommand_PPC.cpl --> \Windows\
VoiceCommandWMP.dll --> \Program Files\Voice Command\
Then ensure that is checked in the settings for MS Voice Command.
Start --> Settings --> Voice Command --> (Highlight) Phone --> Options --> (Check) Announce Incoming Calls
After closing the Voice Command options and a soft reset, you should be good to go.