To win an iPod or the Grand Prize for the billionth song, you must buy a song each time the counter turns 100,000. The problem is: you can't rely on Apple's counter. It doesn't display the real-time count, it makes a projection based on a snapshot of the sales data over a period of 5 minutes, and that projection is always underestimated so that the counter doesn't go up and down each time the new data is released. With their method, it always goes up - but it's not accurate.
The Apple counter also relies on a 100ms timer to keep running, but if your machine is blocked doing something (like dragging a scrollbar in your browser or whatever), it stops and loses count.
I quickly fixed that over the weekend. Here is my page:
http://www.billiontunescounter.com/
It ain't pretty but so far today, it works. That should bring you one step closer to the 10 iPods and the $10,000 gift certificate. Good luck!