I have seen wmpnetwk.exe bug out quite a few times on me, taking 100% cpu usage and/or absurd amounts of RAM.
Whilst it certainly sounds like you have a virus or two, it might be unrelated!
Click the start button, and in the search box type "Services.msc" and press enter
In that list, scroll until you see "Windows Media Player Network Sharing" and disable/stop the service.
Right click it again, and select properties. A window will pop up, and you should change the startup type to Disabled.
You should still try to clear out the malware that your system contains to prevent any other problems.