Hello Rancs,

You mentioned that HDMI does not work after downloading Windows 10. Do you mean to say that you upgraded the OS to Windows 10?
If yes, you may have to check with the motherboard manufacturer whether the model that you have, is compatible with Windows 10 or not. If yes, you may also want to check with them for any updated driver they may have for HDMI. Once you install the same, you should be able to get the HDMI working.

Regards,
Edwin