Some clever folks figured out a way to get 2.0 on your iphone first gen using windows. In fact it was too simple just follow these simple steps and your on your way to app store goodness. iPhone hacks has put up a neat guide which is very easy to follow. Here is a link to the steps iphone hacks
***Update***Here is an official way to PWN your iphone 2g the winpwn way is now officially out for you to play with. You can check it out at www.winpwn.com