Windows lifecycle fact sheet. End of support, End of sales, Service packs and updates

Windows lifecycle fact sheet:
Every Windows product has a lifecycle. The lifecycle begins when a product is released and ends when it's no longer supported. Knowing key dates in this lifecycle helps you make informed decisions about when to upgrade or make other changes to your software.
End of support, End of sales, Service packs and updates

http://windows.microsoft.com/en-us/windows/lifecycle