A lot of people's solution to Windows Media Player trouble is to dump it and use something like Winamp instead.  Nonetheless I got focused on trying to fix a WMP skipping problem that seems to have been around since I upgraded to XP a couple of years ago, starting with WMP 8, later v10. The glitch may have been there earlier, like with WMP 7.1 in Win98 but I can't say for sure.

I still have this old Celeron and am always watching what's keeping it busy and what can be done to lighten the load.  Media Player was just the latest challenge.  I wanted to know why WMP would miss bits of music, no matter what "visualization" I switched to, nor if I set WMP to full or "skin mode", nor if I gave the player high priority in Task Manager.  I also turned off graphics acceleration for the video card.  No good.  Shutting down other programs didn't make a difference either.

I read somewhere that onboard audio could be a factor, how there can be problems to do with hardware acceleration on chipsets that don't have any buffer memory of their own, and that DirectX was mixed in there. So I played around with dxdiag, Microsoft's "DirectX Diagnostic Tool". I disabled "Hardware Sound Acceleration" under the Sound tab, and turned off all port acceleration features under the Music tab.  One of these did the trick.  Windows Media Player no longer stutters tunes.  Yippee!

Now that that's done, I'll probably set Winamp back to being the default player. :)

Stuff I found:
    - How to troubleshoot sound-related issues (Microsoft)
    - DirectX Diagnostic Tool (Windows XP Advice & Information)