WAN Miniport (PPPOE) Problem

Hi guys! I have an old Latitude E6500 with windows vista x32 bit. It had quite an internet problem, but after 2 months, I managed to turn on the Ethernet of the computer. Now I'm looking forward to the wifi. When I enter the Broadband connection, it doesn't work showing Error 815. Error 815 says that the service tag is invalid I then went to device manager and tried to update WAN Miniport (PPPOE) because I haven't updated it in a long time. While it was installing device software, it showed the error: we could not install, they system file is not specified. I also have other numerous problems with my computer, here's an old post: https://www.dell.com/community/Latitude/Please-help-me/m-p/8373710#M48972 Please help in one of these problems please!