For antivirus, just one will be enough. If you are unsure, go for online scans.
For anti-spywares, having a few more on the computer doesn't kill you.
List of Anti-spywaresWMP died on you have a couple of reasons:
1) Too many programs are in used. This will take up a lot of computer resources and slow down the computer. Close any unused programs.
2) Not many programs are in used but one of the programs is using lots of computer resources. Open up Task Manager and go to the Processes tab. Look under the Mem Usage. If one of the programs Mem Usage keeps going up, kill that application and restart it. Be careful when killing the application. Killing the wrong one will result in system instability. Usually those that you can kill include Internet browsers like IE, Firefox and games.
3) If you are playing a song directly from the Internet, check that the file can be played. If not, WMP will hang on you.