How Do You Make Sharing "smart" With Wmp11 On Xp?

So one of the problems that I face is slow system performance, thanks to the fact that my fiancee can't let go of AOL AND likes to use Firefox in conjunction. This already eats up close to a whole gigabyte of RAM out of the 2GB that I have in the machine. I looked at CPU usage through Windows Task Manager (which I know isn't the best out there, but it gives me a ballpark figure), and one of the processes eating up 30-50% of CPU usage is wmpnetwk.exe. Now, Googling this and looking at common sense, the Windows Media Network Sharing service is probably indexing media files in the background, but taking up 50% or more CPU usage IN THE BACKGROUND is pretty unacceptable. Some research shows that WMP might be trying to index a corrupt AVI file (leading to a never-ending cycle of retries), but I don't want to have to keep turning sharing on and off to keep system performance bearable. I currently use that machine as the sharing plateau for movies to stream to my Xbox 360 for the kids, and I was wondering this:

Is there "smart" sharing or is there a way to tell WMP to stop sharing if it doesn't detect my 360 currently being on the network (i.e. the 360 is turned off)? If not, is TVersity resource-friendly? Any other free alternatives anyone would like to suggest?