I found this in a few different places around the 'net - hopefully it's helpful:

Speeding Up Your Pentium 2 by 50%

We all know that you really shouldn't try to run Windows XP on anything less that about a Pentium 3 of some sort if you are out for speedy operations and amazing reaction times, but for those of us with the good old Pentium 2's who want to see just how well we can run XP, we have to tweak as much as we can where-ever we can. A real killer to the system's performance is Windows Media Player. Although it may look desirable and fancy with it's rounded off edges and 3rd-Dimensional appearance, the truth is, it takes up a large amount of that precious processing power. All of these troubles however, lead to one thing in particular with this 'new-look' over-rated music and video player...the Visualizations. The look-great I'll admit but like a lot of software these days, it has no purpose. If you run the task manager, and click the Performance tab along the top, you'll see that when Windows Media Player is running and nothing else is active, it takes up around 50% of the processors power. Once these visualizations are turned off, it barely takes up 2-3% of the processors power, which leaves much more room for other applications to work efficiently.

Here's how to disable the feature:

• Open Media Player.
• Make sure the Now Playing tab on the left is selected.
• Click the View menu along the top.
• Go down to Now Playing Tools.
• In the sub-menu that has just 'popped-out', uncheck Show Visualization.