hijackthis.exe is a process belonging to Merijn Hijackthis and monitors your browsers configurations and plugins. Modifications and restores can be made when necessary. "This program is a non-essential process, but should not be terminated unless suspected to be causing problems. "
Non-system processes like hijackthis.exe originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that over time your registry suffers fragmentation and accumulates invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues