[robby1]

The bootloader is just what the name would suggest, a loader during the boot process. Long story short, it's called from the radio's bootloader once it reaches a certain point and begins to kick off the windows launch process. It checks back to the radio for it's version and is what allows certain key combinations to hard reset your phone or to enter the "bootloader" screen. Once there you can talk to it over a serial or usb link and send basic commands. Nothing you will want to mess with unless you want to learn just for the sake of it (like most technical guys!). One thing it does it flashing the new bootloaders, radios, screen splashes, or roms. Typically from htc is will not flash anything that is not "authenticated" as a official release. But the hard-spl or other spl hacks eliminate this and convince the device it's all ok. Furthermore it checks if the CID of the device (a text string) matches a certain one, and if not might block it. SuperCID is a wild card which unlocks most rom flashes.