Windows 7 can be purchased from the Microsoft website. You can download Windows Home Premium, Professional, and Ultimate versions and download Windows upgrades on the Microsoft website too. In addition to the Windows download, Windows 7 operating system is also available at licensed retailers worldwide.
Windows 8 is not out yet in a commercial release. The Windows 8 Developer Preview was released to the public on September 13, 2011 and is available on the Microsoft website. The Consumer Preview version of the Windows 8 operating system became available on February 29, 2012.
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