How to restore my iPhone 3G to 2.2.1 without updating to 3.0?

I just got my iPhone 3GS and wanted to sell my 3G on ebay. And since jailbreak for 3.0 is not out yet, I didn't want to update my 3G to 3.0. However, when I tried to do a restore on my 3G on iTunes, the only option I get is "Restore and Update (to 3.0)", which I don't want.

So my question is how to restore my 3G to the OS 2.2.1 (which I currently have on my iTunes since I never downloaded 3.0)?

Update: seems like people are selling iPhones with the 3.0 update on there... I guess I can do the same. I'm just worried that it won't go for as much as I would want (at least $300). I know I don't want to go through the effort of unlocking it myself, so I thought I should sell the 2.2.1 version so at least the buyer can unlock it...

BNZ1 said:

It should allready be downloaded from when you installed it. Shift-Restore will do it - http://www.iphonefaq.org/archives/97320

You can also go to Settings > General > Reset > Erase All Content and Settings on the phone.

Click to expand...

lol. where's the EASY button?

thanks for your help.