MS site. It will scan (ask for permission) your hardware and tell you. However that is only official support including the PC manufacturer. I have PCs running both Windows 7 and Windows 10 that "are not supported". The secret is to try it and look for the individual device drivers for your devices. Most PCs will run with the default MS drivers and it is only the better individual device drivers that are needed. For example Lenovo don't support Windows 7 on a T43P, but I can get each of the individual chip drivers from Intel etc.
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