task.exe is a process added by the W32/Randon-Z worm. It connects using IRC to collect commands from an online server. 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 task.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