How do I reset this phone?

Here is how you do a hard reset or factory reset of the T-Mobile G1.

• Power off the G1
• Hold Home Key + End key for 20 seconds or till you see a triangle with an exclamation point and a picture of the G1
• Open the QWERTY keyboard and hit Alt+W

You will see a little animation and it will reset on it’s own from that point.