EDIT 03.14.2012: This one should work: CLICK
Copy the whateveritiscalled.zip to the ROOT directory of your sd-card. Do NOT unzip it, do NOT put it into any folders, just copy it to your sd-card.
Phone is off, press and hold POWER and VOL (+) to boot into the Recovery Mode.
Do a wipe data/factory reset.
Select "apply update from sdcard".
Good luck, have fun and please don't brick your phone!