Join Date: Mar 2004
I did the same with my 2G iPod touch. iTunes automatically updated me to 4.0 when it first came out and I quickly realized that it sucked badly on the 2G. So, I downgraded it to 3.1.2 and all is well.
Search the interwebz and find the ipsw file. For example, mine is called "iPod2,1_3.1.2_7E18_Restore.ipsw". From iTunes, Hold down the Option key (on a Mac) or whatever that is on a PC (Left Shift I think?) and click Restore. It will pop up a window that will allow you to browse to the ipsw and restore from that file.
There may be more to it on an iPhone, so don't take this as gospel but I would think the same technique would get you started. I love my Apples, but shit like this becomes a pain in the ass. Gladly I don't have to fuck with it too often
Hope this helps
93 Cobra #199