Can I revert my iPhone 3G back to the original OS it came with when I bought it?

I've had this phone for over 2 years now, and I have to say it's been getting slower and slower with each update I've installed to it. Lately, I installed iOS4 and now it takes 10 seconds to open up my SMS, (which is my primary app I use).

I'm very irritated by this and I would like to reset the phone back to the original OS it came with when I purchased the phone two years ago. Is this possible? If so, how?

Thanks,

-Heff

yes it is possible...sometimes.

Its largely dependent on exactly which hardware you own and whether the hackers out on the tube-o-sphere have developed a downgrade for that hardware. Bear in mind that there are hardware revs for each iphone model. In other words there are multiple versions of the iphone 3G. They are not all exactly the same.

Anyway, just do a google search for iphone 3g downgrade (or whatever model you have but I'm betting on 3g given the timeframe you've stated) and you'll find a wealth of information. Be warned, some of it gets a bit techy

inborg answered

An addendum because I'm not sure if you'll be able to downgrade all the way to your original OS (likely something in the 2.x family) but you should at least be able to go from 4.x to 3.x which may or may not be to your liking.

instructions here: How to Downgrade Your iPhone 3G from iOS 4 to iOS 3.1.3