Unable to boot ubuntu 12.10 due to graphic driver problem with ati HD6470M card. Sony vaio VPCSB36.Please help

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http://askubuntu.com – After installing the latest drivers for enabling the hybrid graphics mode, my system collapsed and since then I have not been able to overcome the "LOW GRAPHICS" problem. I have uninstalled the graphics drivers but even then the problem still remains. Please help (HowTos)