icculus, under PowerDVD there are audio settings to choose from two channels, four channels, six channels, and SPDIF. If you bought or have PowerDVD XP 4 with the dolby digital package, then you should play DVD movies in full 5.1 dolby digital sound with out any problems. Most sound cards can not output more than four analog channels. Other sound cards use Direct Sound to handle the rear channels. Try buying either Audigy or LIVE! 5.1 from creative labs. Audigy sound cards has some problems.
I have used a AMD 800 MHz (Slot A) on a ABIT KA7-100 with PowerDVD XP 4 and I had no problems. The only problem that I had is ATI's drivers. Their drivers kept on halting while starting Windows 98. I had no problems using LINUX radeon drivers from X86free. Since my motherboard quit working from the lack of filtering, I had to get another motherboard. Yes, capacitors leaked orange oze (paste).
To make using an AMD based computer easier to setup. Many motherboard manufactures are including Winbond (system diagnostic chip). If a part has a conflict, the Winbond will show a BIOS code. Then the user looks up the code in the motherboard manual to see whats the problem. The only motherboard manufacture that I know that has winbond on an AMD board is
EPOX. Many other manufactures are following EPOX.
BTW, computers that come with DVD software players does not always have the latest version. I suggest you upgrade to PowerDVD XP 4 with Dolby Digital package.