By Neil Hughes

Published: 11:45 AM EST

In a new research note to investors, Piper Jaffray has forecast that Apple's new Snow Leopard operating system will sell 5 million copies during its launch window in the September quarter.

Senior Research Analyst Gene Munster believes the sales will bring Apple an additional $66 million in operating revenue during the quarter. However, he believes those totals are already "baked in" to Wall Street's own numbers, given that the sales window and $29 price of Snow Leopard were already known earlier this summer. The $66 million in income would amount to 5 cents in earnings per share for the quarter.

The $29 price point is designed to put a dent in sales of Microsoft Windows. He said the finely tuned operating system upgrade will be used to portray the Mac platform as superior to Windows machines.

"The release of Snow Leopard is not about new features; rather, it is about keeping Mac users up to date with the latest technology vs. Windows XP and Vista users on antiquated technology in our opinion," the note reads.

Munster believes that Snow Leopard has an advantage over Windows because it comes with support for Microsoft Exchange built in. Out of the box, Snow Leopard machines will support Exchange for e-mail, contacts and calendars, and the overall system will run faster when compared to Leopard.

The new note estimates that there is a OS X install base of over 40 million. For comparison, Apple sold 2 million copies of Leopard in 4 days to a install base of about 23 million OS X users in October of 2007. For that launch, Apple sold a total of 3.5 million copies for the quarter. At that time, customer satisfaction with Leopard was said to be driving explosive Mac sales.