Default How do I reflash the original ROM on my touch dual?

Hey Everyone

Just received my Touch Dual, but it's got an Optus startup screen and I'm a Vodafone user!

Just wondering how to re-flash it with the orignal non-network personalised software, just standard Windows?
Where could I go for this software (it's not on the HTC support area at all!)?

And is it hard to install?

Thanks HEAPS!
Mike