Hi, i downloaded the quest engine but when i try to open a .quest file i got this error, someone knows how to solve it?

Looking in my registry, that clsid is for SAPI, the Microsoft Speech API. I know Quest can use it, but I don't know if Quest installs it or assumes it's installed already.

Here is one page talking about it: http://www.nextup.com/sapi.html4

What version of Windows is this?

I was reading a thread recently where HK found a solution for an issue where the Quest editor returns an error when trying to load a game if xp is the os. can't find it again now though.

Yes, that had to do with the version of .NET:

viewtopic.php?f=10&t=4437&p=29604

It looks like a different problem.