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How come ISO file with installation of MSVS 2010 Express (All-in-one ISO) is 693MB compared to when I mount the ISO, copy all the contents to folder on disk and that folder is 1.6 GB? If zipped this 1.6 GB folder goes down to 1.55 GB archive.

What I am missing? I thought ISO is just a image without compression. Thanks!

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up vote 2 down vote accepted

ISO files can contain multiple references (by filename) to identical files in different folders. The ISO file itself only contains one copy of the file.

Upon extraction, duplicate identical files are being created.

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Thank you very much. – NeverStopLearning Feb 26 '13 at 13:59

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