NOTE: This video was taken and posted on 2012. This may and probably not going to work with modern Android OS! Many of you are complaining that it require root, in fact, there is no root command used in the CMD as shown in the video and does not require root access. Again, if it is not working for you, it does not mean that it will not work for others.
This solution is provided by m.sabra @ XDA
Should work on Android 2.1 and above. This solution won’t work in recovery. Make sure USB debugging is enabled and allow permission (4.3+)
*Debugging mode must be on
1. Plug in your phone cable
2. Go to ADB
3. Type the following commands:
adb shell rm /data/system/gesture.key
4. Reboot your device.
5. Draw any pattern to unlock the screen.
6. Go to setting menu and change the screen security to slide.