Factory reset not working on Galaxy 10.1 tab

I have a galaxy tab with following specs Model number: GT-P7510 Android version: 3.1 Kernel version 2.6.36.3 se.infra@sep-58#1 Build number: HMj37.UEKF3 P7510UEKF3 I have tried -- Settings > Privacy > Factory reset -- Powered off the device -> Up Key + Power button -> Recovery mode > Factory reset , but its not resetting the tab to factory settings, After restarting its always showing me already installed applications and gmail/facebook account.