Chris

Problem with copying the Vista 5728 iso file to external hard drive

I downloaded the 5728 iso and checked its MD5 using DigestIT.
The MD5 was correct.
Then I copied the iso file to an external hard drive.
The filesize was correct, but the MD5 was different.
I copied it three times to the external hard drive.
Each time the filesize was correct, but the MD5 was different.
Any ideas?
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Chris