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On my PC, I open winzip, select Open Archive and select the tar.gz. It normally says "archive contains one file, should winzip create a temporary folder and decomress it?" I say yes. You should see a list of files appear in winzip window.
Then select Actions/Extract. For safety's sake (so you don't wind up with a hundred files on your desktop) I create a temporary folder and select that as the destination. Ensure 'Use folder names' is ticked.
Some developers bury the actual module folder several layers deep, so mymodule124.tar.gz could extract to mytemporaryfolder/mymodule 1.24/html/mymodule. The last folder is the one to upload to the modules directory. It should contain a xoops_version file.
Actually, extracting tar.gz files using winzip is good, 'cos it automatically strips out erroneous line feed characters in PHP files that have been created with Linux and Mac text editors.
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