samsung galaxy tab freezes and won't reset to factory settings

Please help!
I've bought a Samsung Galaxy Tab 7.0 Plus and after my daughter downloaded a load of Apps have found that it keeps freezing. I then have to wait 12 mins until it will switch back on again. I have tried uninstalling all the Apps individually but they come back. I have also tried resetting back to factory settings and it appears to be working then it freezes again and when it does switch back on everything is still there. What can I do to stop it freezing and to reset back to factory settings?