1. Use appcmd.exe to recycle the application pool from the command prompt.
2. appcmd.exe is the command line tool for IIS7, you will find this tool at following location :
%systemroot%\system32\inetsrv\appcmd
3. To recycle your application pool use the following command:
appcmd recycle apppool /apppool.name:<application pool name>
Ex.
appcmd recycle apppool /apppool.name:"Sharepoint - 80"