I have never rooted my phone before. I don't know what the guy who owned this phone before did.
rom type
mgb, android ver 2.3.3, rom ver 1.1.2
Does that help?
Let's try this: First, make sure that your battery is higher than, say, 50%. If it is not, plug in the phone while you do the following:
power your phone down. While the phone is off, hold the VolumeDown key while you press power. Hold power until you see the screen light up.
It should start a special low-level HBOOT, with a white screen with a text menu. It should look something like this, though not exactly like this (I hope):
Can you type what the first two lines of that display are? (Actually, all you have to say is whether the top line says "S-ON" or "S-OFF" and what the numbers are after "HBOOT" - it will be either 1.46.0000, 1.47.0000, 1.49.0000, or 1.49.2000 (which it will only be if the top line was S-OFF.)
There should also be something that says "Press Vol Up for Recovery" (perhaps not those exact words.) Press the volume up key and the phone should vibrate and take a few seconds to start something else.
When it does, does that something else look like this:
If yes, notice there is a menu item highlighted that says "Reboot system now". Just press the trackball to do that and restart the phone; it will start normally.
If no, does it say "ClockworkMod Recovery" on the top line?
Also, do you have a Windows PC or a Mac?