I would suspect you can do it using the power and volume keys, but it could be a little tricky.
Does it make sound when it boots, etc?
You can try this, and see if it works. This is from a Sprint phone, and I am not sure if the menus are identical across carriers, but I can check another carrier to see:
1) Press volume up, home, and power at the same time. After you feel the phone vibrate, you let go of power, but hold the other two for about a second more, then you can let go of them all.
2) give it a few seconds to boot - 30 maybe.
3) push volume down 3 times to get to wipe data / factory reset on the recovery menu.
3a) if you want to wipe the cache prior to the reset, push volume down 4 times, then push power. Give it a minute or two to work, and then it'll come back to the recovery menu. After a minute, you will then push volume down 3 times to get to the factory reset menu item.
4) push power, which takes you to another "are you sure" type menu.
5) push volume down 7 times that puts you on the "delete all user data" menu item.
6) push power, and the factory reset will begin
If the factory reset was successful, you'll feel it reboot again after it completes. It may take a while to boot after it resets, so give it a little time. After you feel the vibrate, it will still run awhile after the initial boot to complete the reset - give it some time.
If you can see it on your computer, then you can check to see if it has reset.
If it does not reboot after awhile, you haven't gotten to the correct menu item, so you can pull the battery and start over.
Also - this is a Sprint phone, running 4.1.2.
What carrier / version do you have?
