from froyo back to 2.1

[solidgeter]

I recently installed froyo manually before i knew anything about rooting and roms and what not. But i cant find a tutorial that explains how to root a phone that already has froyo installed on it. Im guessing I have to go back to 2.1, root, then install the rom I want but I when try to run the update file for 2.1 its a no go. Any suggestions?

Much appreciated