That's not a firm standard and what you should discover is some CODEC could fail, leak, grow. I know some won't want to read that MSFT does not consider bugs in CODEC they didn't provide something they need to fix.
That's my bet. It's the codec leaking. Good luck trying to find a MSFT sympathetic ear.
I was looking around in the forums after I found that wmpnetwk.exe was taking 1.5GB of my 2GB of RAM, this is a problem that was never addressed with in the designing of Windows 7. I can't tell if it's using alot of my CPU power also because I have F@H on most of the time but I read that was also affected. I will be streaming media to my Xbox when the update for Media Center is released which will have Sky Player functionallity, so I want to leave that service enabled. I don't use .avi files either, only .mp4 and .wmv, so what is making wmpnetwk.exe use so much memory?