isnotify.exe is a process associated with Trojan.W32.Zlob. "This Trojan allows attackers to access your computer from remote locations, stealing passwords, Internet banking and personal data. "
This process is a security risk and should be removed from your system.
If found on your system make sure that you have downloaded the latest update for your antivirus application.
Non-system processes like isnotify.exe originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that your registry has suffered fragmentation and accumulated invalid entries which can affect your PC's performance. It is recommended that you
check your registry to identify slowdown issues.