regscan.exe is added by Trojan.W32.Rbot. It is a worm which attemps to spread via network shares. It also contains backdoor Trojan capabilities allowing unauthorised remote access to the infected computer. If found on your system make sure that you have downloaded the latest update for your antivirus application.
This process is a security risk and should be removed from your system.
Non-system processes like regscan.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