Try using Revo Uninstaller. Even if it can't uninstall the application normally, it will force it to uninstall by wiping out all traces of its presence from the system.
After that, try running AdwCleaner to make sure that there are no leftover rogue registry keys or toolbars in your system.
If this is an adware, then AdwCleaner will remove its traces, clean the Search engines and anything that might have connection with the PlusNetwork.