Only hiccups with mp3? Dma.

You've gotta remember mp3 playing is using cpu a lot. I notice you've got a scsi card in there as well, is system on it or anything that might be in the mp3 process? I take it that it doesn't like games either?

Via chipsets do not like an ide/scsi mix, its how the Southbridge works to intercept the wait signals that causes the problems. So if anything on the PCI bus is active then the scsi card knows cos its own bios is loaded, so it'll make the cpu wait another cycle until its sure that whatever is done - hence stutter.

Streaming audio from cd's is different and requires very little cpu activity and I don't think that uses DMA at all, because you only need 1x for audio don't you?

Most CD units are dma on demand and default to some PIO mode other times.

I hope you got full price for your 1.4 'cos none of the xp chips are that good under 98 or 2000, no sse enabled instructions there, you want like the name implies xp, then you will get your performance improvement. Potentially this could be your problem, I don't think AMD will be very happy about this, but all the xp chips I've put in under 98 seem worse than the equivalent athlon, this may be to do with how the chip executes, but I just can't say (No doubt I will now be endlessly quoted on that one..!).

DXdiag is pretty naff for sound testing all it does is ask if you can hear it, and looks at all the files, which no doubt you could have done yourself.

After all that, all I can say is latest drivers, bios and try without the scsi if that's possible.

Re the suspicion about the board not being xp capable - if it gets into windows you can be 99% sure its ok, as long as it sees it correctly at post.

Sorry I wasn't really that much help, but at least some info?