Wow, I think everyone here had no problem reading your single sentence original post. If regurgitating your first post is your way of providing additional information to people actually trying to help you then have fun.
well he has a PM G4 so i guess he is trying to expand two discs to look like the one physical partition. easily done.
chuck in your OS install disc, boot it up, launch disk utility. erase the HDs (zero is recommended). configure them as a raid device and choose the one that lets you stripe the data. simple.