ismon.exe is associated with Trojan.W32.Zlob. This Trojan may open links to pornographic websites and also attempt to download and run files from a remote location. This process is a security risk and should be removed from your system.
Non-system processes like ismon.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