I made a post about this a while ago. I don't think it's easy to go down from iOS 2 to iOS 1. But please let me know how it works for you. I have an original iPhone on iOS 1 and I love toying with it and remembering the good ole days 🙂
Just tested it on my iPhone, it was very easy for me to go down from 3.1.3 to 1.1.4, just DFU & Restore with iTunes 7.5 on freshly installed XP. It was done the first time, no errors (just the baseband error but that's normal, solved with iBrickr 0.91).
But i see that is not so simply to restore iOS 2.x, i don't know why. It's possible, because i have have now 2.2.1 on my phone, but it's a little trickier than 1.1.4.
To install 2.2.1, i downgraded to 1.1.4 and than shift-restored a custom firmware (created with PwnageTool 2.2.5) with iTunes 8.0.2. and the iPhone powered on, no DFU or Recovery. No errors, just fine.
I tried restoring 2.2.1 in DFU but iTunes gave me the "iPod software update server could not be contacted" error, while it worked with iPhone powered on normally. Apple logic.
🙄
For these tests, i suggest this method:
create a fresh, clean XP install in VMWare (or other VM platform). Then install just the drivers & VMWare tools. Reboot and than take a complete system snapshot
BEFORE installing any other software on it.
So, if you have a problem with iTunes (and i'm sure you'll have
😀), just restore the snapshot in a few seconds and you're ready again.
With this trick, it's possible to test different iTunes versions without the hassle of removing it every time (iTunes for Windows is kind a crappy software, is difficult to remove completely)
PS. Sorry for my english, i'm from Italy & still learning
😛