hey, i found this tool that might help you.
it fixes regisrty problems with sapi.
it doesn't do anything with the registry except sapi issues.
it is clean, and it works. no virus, no extra registry stuff, just clean code.
hope it can help. i have used it to fix issues that some sapi voice installers create.
http://cid-7d1b0521931256f1.skydrive.live.com/self.aspx/.Public/Other/FixRegistry.zip
Can it really fix sapi voice installers. Send me some info if you have the time.