I don't think that it needs to be run in dosbox. AGS games run in windows properly. Um maybe I'm wrong, cos that version looks like the dos version of AGS.
That error is showing something wrong with the speech pack. Maybe you didn't install it properly or something. I think it worked for me, and many other people.
If you can't work it out, you could try making a post on the AGDI forums.
edit:
I think maybe this is your problem... The version of KQVGA on this site seems to be 2.0. On the AGDI site, they have version 3.0. If you are using the speech pack corrosponding to the wrong version then it might not work. I suggest getting the game and the speech pack from
http://www.agdinteractive.com/KQ1.php