Sorry to hear that, even I am "lucky" user of MX300 on KT7A, there are lots of pplz are having problem with that combo. I am using Aurial's refference drivers and have no problems at all, the main thing is the process of installation. If you will do that in certain order, it should work fine, but maybe you have some different thing that is conflicting with it.
I can't tell you each step at a time, but basic idea is to install everything and then open Device manager and update driver for the PCI blah blah multimedia thing, point it to the Vortex reference drivers (I got them from vortexsound last winter, reboot right away, hopefully enjoy.
About DVD playing, it depends on the software you are using with DVD. When sound card is installed, it is installed no matter what, but some programs could not initialize it properly with Windows, so it could be something weird going on. I did not have any problems with it while playing DivXs, but did not try with DVDs (I don’t watch DVDs on the PC, there are better things for that
Anyway, I've tried different PCI slots, it works in 3 best, but different people could say different things. So just play with it for a little, don’t give up soon, it is really fine card when it works, I did not hear anything better yet, but it is just me )
At this point I took it off the KT7A and put it on CUSL2-C (my main gaming machine) and it works there very well, even tons of guys had problems with i815 and MX300 combo as well.
I have to agree with blah on this one. I just recently upgraded my system. I've had my MX300 for a while, and never had any problems. But after upgrading to an Abit KT7A with an Athlon 1.2, I kept getting system hangs at the strangest moments -- while playing movies, while surfing the Web, while starting up games, etc. After wracking my brains for a couple of days and trying anything and everything, I finally narrowed it down to a conflict with my MX300, and that's when I came to these boards and discovered other people having similar problems.
But now it all seems to work fine. The solution? As blah said, you need to use the latest Aureal Vortex 2 reference drivers (v4.06.2048), as opposed to the last drivers provided by Diamond (their v1.02 release, which actually only included the v4.06.2017 reference drivers from Aureal). For the reference drivers, go to a site like www.vortexofsound.com and download them. Then uninstall your current Vortex 2 drivers (either if you'd already installed the Diamond ones beforehand, or if you're running an older version of the reference drivers) from the "Add/Remove Programs" (look for the "Aureal Vortex AU8830" item in the list) and reboot. When it detects a "PCI Audio Device" upon booting up, point it to those latest reference drivers you downloaded and unzipped, and everything should work.
I even had my MX300 in PCI slot 2, not slot 3 like blah suggested, and it still works. I somehow doubt the slot has much to do with it, unless you're using one of those quirky slots (like slot 5 in a RAID setup, which shares an IRQ channel with the RAID controller). I don't even think the order in which you install your various drivers matters too much. But, for reference, I installed them in this order:
1. VIA Service Pack (from Abit's CD)
2. VIA USB Driver Update (from Abit's CD)
3. nVidia Detonator3 Reference Drivers v12.41 (for my Canopus Spectra 2500 (a TNT1 video card))
4. Aureal Vortex 2 Reference Drivers v4.06.2048
Anyway, so far everything seems to work pretty well for now, and I'm really glad I didn't have to ditch my MX300, as it really is a nice card.
Hope that helps anyone else having similar problems...
Using the Aureal reference drivers is the key. There is also an update driver as well. I used slot 4 for my Aureal Vortex2 SQ card (basically the same as the MX300) and had no problems.
Currently, I am running a Hercules Game Theater XP sound setup and no problems so far.