I was able to shut the phone off by holding the power button down for a long time without touching the volume control... See the update in my first post.
Prior to the black screen, I was just browsing a car forum using the android browser. I want running any other apps or downloading anything. I left the phone for 3 min which is long enough to turn off the screen, but instead of going to the lock screen when I tapped the power button it just didn't respond. To clarify, the screen didn't just go black while I was in the middle of using the phone, but rather once the screen shut off as it should after a few min of inactivity, it became unresponsive (except for the home button flashing when I held down the power button).
Yeah, I'm new to android, in fact this is my first smartphone.
How do I turn off fastboot (and what does that do, exactly)?
How do I turn off HTC sync but leave Google backup on?
And what exactly does holding the power button plus the volume up button do? Will I lose any data when I do that?
Sorry for the noobishness and thanks for the help.