"But Windows XP has the most market share out there! (A whopping 44%) Of all operating systems on the planet, it has the most"
I think that's only true if you include Asia, where there is massive use of pirated XP.
According to NetMarketshare.com
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Nth. America: XP: 26% Win7: 48%
Sth. America: XP: 34% Win7: 54%
Europe: XP: 32% Win7: 46%
Australia: XP: 23% Win7: 47%
Africa: XP: 39% Win7: 51%
Asia: XP: 57% Win7: 34%
In all regions other than Asia, use of XP is falling steadily and Win7 rising at the inverse rate.