realpopup.exe is a process belonging to the Real Popup utility which is bundled with RealPlayer. Also belongs to the RealPopUp (predecessor to WinPopup, a network messaging tool. In both cases this program is non-essential process to the running of the system, but should not be terminated unless suspected to be causing problems.
Non-system processes like realpopup.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