The SHA1 hashes for all Windows 8 ISOs are available from
MSDN. Click on the "Details" link to see the correct Windows 8 ISO file names and corresponding SHA1 hash numbers. A very concise tutorial on how to download/create an official Microsoft Windows 8/8.1 ISO image is available from
EightForums. I prefer to use SlavaSoft's free
HashCalc 2.02 for verifying download integrity. The checksum of your current DVD can be verifed with the free version of
WinISO 5.3. First use WinISO to create an ISO image file of your current Windows 8 DVD and then use HashCalc to verify the integrity of the ISO image.
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