- Try entering "null" as password. (together with your Google username)
- Create a new Gmail account on the computer.
- Call your cell phone with a different phone.
- Answer your cell phone then hit the back button and it will take you to the home screen.
- Turn on WiFi so it can do data and voice at the same time (remember that the phone is still connected)
- Go to Settings -> Location & Security and disable lock pattern (you'll need to enter to correct pattern previously set)
- Go to Settings -> Accounts & Sync and click "Add Account" and add your newly created Gmail account.
- Disconnect the call and switch the phone off.
- Turn the phone back on, at the lockout screen, enter your new Gmail account info and it should let you back in
- Once the phone is unlocked, you can go in setting and remove the newly added Gmail account and keep the old one.
- Factory reset your phone (links to Android device manuals can be found below, it differs between devices)
- Setup your phone just like you did the first time you unpacked it (use the same Google Account if you want your old contacts back!)
- Restore any manual back-ups and install your previous applications from the My Downloads list.