Sure, those visualizations look sweet while you're nodding along to your favorite song, but how often do you really use them? And do you really need that skin that replicates the faceplate of your car stereo down to the tiniest detail?
You should ask yourself these questions because, when it comes down to it, the reason you use a media player is to listen to music or watch movies. If you're watching the latest flick, you're not going to need a fancy skin or visualization suite anyway -- chances are, you'll be watching the movie in full screen mode. And in this age of multitasking, most users run their music in the background while surfing Youtube or checking their e-mail.
Clearing out your plug-ins could improve the performance of Windows Media Player by a considerable amount, and CPU usage should drop accordingly. With Task Manager open, run your Windows Media Player with all the bells and whistles, then disable them and run the program again: You should see a marked difference in CPU usage, freeing up valuable resources for everything else you do while you're online.