VPN.AC Client Software window still shows after uninstalling

[yabi]

Hello, a few years ago I was using openvpn. I haven't used it for years only because I do not have the need anymore. I am running windows 7 on this computer. I am giving the computer to a friend, so I am trying to clean it up as much as possible for him. I did uninstall the openvpn program but still upon start up of the computer, a small window pops ups. The title of the window is "VPN.AC Client Software". In the window itself it states "OpenVPN initialize error". I would like to learn how to remove this window from coming up upon start up. Can anyone help with this? Thank you.