Once again that wonderful company you all know and love decide to run riot over the rest of the world.
There are two definitions of a cm - Microsoft's and everyone elses...
http://support.microsoft.com/?kbid=189826
In other words and for those who can't bothered to click the link. Micrososft don't like a centimetre to be the size it is as it makes their program work incorrectly. So they'll change it.
From now one the world according to microsoft defines a centimetre such that 1 inch = 2.4 cm as opposed to the International standard of 2.54 cm
And you guys wonder why I don't like them very much!