if your using intel chipset mb it because windows 7 iso does not have the chipset drivers for the newer mb. you have three options. try at start up of windows 7 install hit f6 see if you can install chipset drivers. if you cant try using 3 party program like 7lite to add updated drivers to windows 7 iso. maske a new iso image. the last and easy is download windows 10 and use classic shell to make windows 10 look like 7. if you have a valid windows 7 key contact microsoft see if you can still get the free upgrade.