What is it?
Microsoft Windows Media Player - wmplayer.exe
What does it do?
This is an exe of the Windows Media Player which since its bundled with windows is the most common application out there for playing music and watching movies. If this process is running and you're not viewing or listening to any media then this is quite likely a BAD process that you should knock out right away. Even if it is the Media Player you can easily end the process without anything bad happening to your system.
You'll want to keep an eye on this google search for any known viruses. The normal location of this file is C:Program FilesWindows Media Playerwmplayer.exe