winnet.exe is an add-on for the Internet Explorer allowing you to search for sites related to a specific keyword. This process is an adware and is know for using large amount of system resources.
Non-system processes like winnet.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