To my knowledge, Microsoft doesn't make Windows 7 ISOs available to OEM users any more, however I have some old disks laying around of Windows 7 burnt from ISOs. Problem is I can't remember where the ISOs came from, and especially whether it was a reliable source. Does anyone know how I can check if the copy of Windows 7 on the disk is original and untouched? I've heard something about checking hashes, but can't find elaboration. And is there any other way?