first of all, to update to the 2.15 radio you need to have s-off. if you haven't done that yet, you need to do it first.
second, if you don't know what hboot is i gotta ask this question: are you rooted yet? because if not, you need to do that before anything else...
the way i always get into hboot (aside from using quick boot, which i do a lot as well) is by holding down the trackpad and power at the same time. this will bring you into a fastboot menu with a few options, the first of which should be bootloader...press the power button on bootloader (which should already be highlighted) and that will take you into hboot. it will check for PB31IMG.ZIP in the root of your SD card...if it doesn't find it, it will put up a bunch of error messages...if it does find it, it will ask if you want to go ahead with the upgrade.
in summary, these are the steps to upgrade from stock radio to 2.15 radio:
- root phone using unrevoked3 (not sure if you've already done this):
unrevoked3 recovery reflash tool, v3.1
- install unrevoked forever using these instructions (make sure you read EVERYTHING first):
public:forever [RootWiki]
- once you've verified s-off, then you can flash the new radio by downloading the image and putting it into the root of your SD card, then booting into hboot and letting it detect the file and tell it to go ahead with the upgrade
make sure you do a backup before running forever, and another one before flashing the radio.
also, i mentioned quick boot earlier in my post: if you're already rooted, you can download an app called quick boot from the market and tell it to boot into the bootloader...that should reboot and take you directly into hboot.
