I've encountered multiple specific problems hence why the thread title is "multiple problems".

So it all started when a recent Windows 10 update was installed on to my brother's laptop. Laptop restarted and did not boot up. Encountered a srttrail.txt error. Read many posts on this. I tried bootrec, bcdedit, startup repair, chkdsk, scannow......the laptop always got stuck at a blank black screen or could not repair the startup.

I downloaded an ISO from the microsoft site to try and re-install Windows, burned it to a dvd at max speed (using my laptop), then booted it on to my brother's laptop under Legacy Boot mode. It booted well except it could not accept the product key which came with the ISO file (which came from a site that was partnered with Microsoft). We checked the product key multiple times....no success. I tried downloading a pre-activated ISO file to bypass the product key screen and I get to the "Select driver to install" screen telling me I am missing a media file. I downloaded a chipset onto a usb drive and selecting it but the laptop keeps saying "Could not find any drivers".

So.....is the ISO corrupted? Did I burn the ISO too fast? Is the DVD scratched? Do I need to edit any settings in BIOS? This is an Acer laptop with an i7 processor.

By the way, By brother downgraded to Windows 8.1 because he used somebody else's Windows 8.1 cd to repair his computer.....or at least that's what he told me. Anyhow, his OS is now 8.1.