want to use a HTC desire on softbank

[Guest ext23]

hi all, this is my first time in a forum like this so please be gentle!

i have been using an iphone 3G on softbank for the past year or so. however rather fortuitously i managed to smash the screen and now it's time to get a new handset. i went back into softbank and asked about price plans for the HTC desire and the new iphone 4. turns out the HTC is ridiculously expensive to buy from softbank in japan and it doesn't qualify for the iphone's packet-houdai discount, either.

so here's what i want to do:

buy an unlocked HTC desire from some other country and use my EXISTING iphone 3G SIM card with packet-houdai with it, with the same phone number and email address (@softbank.ne,jp).

my first question is, is my old iphone 3G SIM card even compatible with the HTC? and if so, will the standard HTC handset (such as the one sold by clove) be able to run on softbank's 3G network (i understand japan uses different frequencies than other countries)?

can somebody please list all the steps involved? as far as i can tell, it involves rooting the HTC, and then applying some custom settings/apk files to enable softbank functionality such as MMS?

thanks in advance, keep up the great work on this forum.