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Steam has now officially stopped supporting Windows 7, Windows 8, and Windows 8.1.
(www.theverge.com)
This is a most excellent place for technology news and articles.
It was during this time the transition to 64 bit systems became necessary to deal with needing to have more than 4GB of memory which was not helped by Vista using 2GB just to run, iirc. If you ran Vista 32 bit you had memory problems. If you ran Vista 64 bit you had major compatibility problems. It wasn't until the end of Vista's life did 64 bit go mainstream.
What can I say? I had a laptop with Vista pre-installed and it was fine.