the command set so the hardware that was manufactured as XP compatible was NOT Vista compatible. Then they didn't include enough drivers to over come that in the initial versions of Vista. Add in they didn't give the hardware companies enough lead time to make Vista compatible hardware, and you got what happened - software that didn't work well with much of the hardware.
By the time things had progresses to the drivers and compatible hardware being available, most people had given up on it. And the root cause was a deliberate arbitrary change of the command sets by Microsoft - in short, they shot themselves in the foot in an attempt to force change on people.
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