If you install the Android SDK on your computer, you can connect the phone via USB and use the
adb tool to perform a factory reset on your phone. That will erase all your data. You can also use
adb to retrieve files and data before doing the wipe.
To retrieve files, type the following at the command prompt / terminal on your computer (make sure it's running in the directory where you have the SDK):
./adb pull phone-file backup-file
./adb pull /sdcard/DCIM/myphoto.jpg C:\backups\myphoto.jpg
And to wipe the phone:
./adb wipe data
You might need to try some variants of that, and on some phones you will unfortunately need to be rooted.
More info on adb: http://developer.android.com/guide/developing/tools/adb.html
Edit: There's a better way to do a factory reset! It's harder without a screen, but not impossible.
- Power the device off. If the device is unresponsive and does not turn off, remove the battery and then re-insert it.
- Press and hold the Home key and the red End key for 30 seconds, the release.
- Wait a few seconds, then press the Home key and the Power key again.
- Wait 30 seconds, then press Volume Down twice. Click the Power button once.
- Give the phone a few minutes to do the factory reset.
With-screen instructions are here.