1- Open Root Explorer & navigate to /system
2- Now Open build.prop in Text Editor.
3- Edit ro.build.version.sdk = 16 & save.
4- Now go to /system/app & Rename GoogleQuickSearchBox.apk to GoogleQuickSearchBox.apk1
6- Now edit build.prop & change ro.build.version.sdk = 15 & reboot.
Now any time you fiddle with your phone, you risk screwing it up. So if you're going to do this, make sure you absolutely know what you're doing. If you do, let us know how it works out in the discussion. [XDA Developers via TechCrunch]