Windows Division revenue growth is largely correlated to the growth of PC purchases from original equipment manufacturers ("OEMs") that pre-install versions of Windows operating systems because the OEM channel accounts for approximately 75% of total Windows Division revenue. The remaining approximately 25% of Windows Division revenue ("other revenue") is generated by commercial and retail sales of Windows and online advertising from Windows Live.
Windows Division revenue increased due to strong sales of Windows 7 and PC market growth. We estimate total worldwide PC shipments from all sources grew approximately 9% to 11%. OEM revenue increased $1.8 billion or 93%. Including revenue and units associated with the Windows 7 Deferral in the prior year, OEM revenue increased $364 million or 11%, while OEM license units increased 5%. The OEM revenue increase was driven by PC market growth, PC market strength among business customers, and the mix of versions of Windows licensed, partially offset by lower Windows attach rates in China and year-over-year changes in inventory in our distribution channels. Other revenue increased $125 million or 13%, driven primarily by commercial and retail sales of Windows 7.
Windows Division operating income grew as a result of increased revenue, offset in part by higher operating expenses. Cost of revenue increased $22 million or 5%, primarily driven by higher traffic acquisition and royalty costs. Sales and marketing expenses increased $22 million or 4% reflecting advertising and marketing of Windows and Windows Live.