It's possible to disable WMP from startup:
1.
Start>>Search>>Services.msc,stop and disable service
Windows Media Player Network Sharing Service
2.Go to Control Panel>>Internet Options and see figure:
ImageShack - Hosting :: wmpdisabledkw7.jpg
disable options which I showed
3.Go to
HKCU\Software\Microsoft\Windows\CurrentVersion\Run and remove value
wmpnscfg from this key