And it was when iTunes came to Windows that the iPod took off in sales (ironically, reversing a LONG trend by Jobs to keep Apple products on the Apple platform). In 2002 and 2003 they sold less than a million units. The first quarter they had iTunes on windows, they moved over 2 million units--more than double what they'd sold the previous holiday quarter.
People look at the iPod as this huge instant hit. It wasn't even 'till Q4 2004 that Apple sold more than 1m units in a quarter. And sales in 2005 came in a large part from selling through Wal-Mart, too.
http://support.apple.com/kb/HT1353 identifies the iPod (Click Wheel) as their 2004 model.