Amazon.com started accepting pre-orders for Mac OS 10.6, or Snow Leopard last weekend, and the upcoming OS has shot to the top of the Software sales list. Two different incarnations are currently 1 and 2. The $29 single-license upgrade is #1, and the $49 5-user family upgrade is #2. Sadly for Microsoft, it’s Windows 7 Home Premium Upgrade is down at #13. However, Microsoft Office Home & Student 2007 is #3.  Additionally, Microsoft Office 2008 for Mac Home & Student Edition is at #4. The top five