Hi There
I have this card and have perfewct playback.
The first thing to check are the M0-Audio drivers you are using. I recall about 18 months ago, there was a severe issue with this card and DVD playback software TheaterTek. It was necessary to have a verry specific set of drivers to make everything work.
Unfortunately, I'm away from my HTPC at present so cannot tell you what drivers I use but check out m-audio website and search for various downloads (check the Beta checkbox to get all options).
Download a few of the more recent driver releases and install, restart & test. Note M-Audio provide a driver uninstall utility. Make sure you use that!
Next, run MC without any DPS effects switched in. I found in experimenting that some combos could cause problems.
Make sure you are using ASIO as your playbak settings. This bypasses windows sound mixer junk and pushes audio directly to the card using a professional protpcols.
Finally, eliminate junk from your PC by following some of the Win XP optimistaions tips you can find on the internet. There is SO much junk in WinXP that you don't need and disabling many services, optimising registry entries etc. can boost PC performance significantly, helping audio and video applications run much better. (You need to be confident you know what you're doing though and always make backups!)
Peter