Unable to boot Ubuntu Properly

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http://askubuntu.com – I have AMD Radeon 7470M 1GiB garphics card. I installed Ubuntu in the nomodeset, after my first boot, I just opened it from boot screen by pressing 'e' and replaced “quiet splash” with "nomodeset". It worked fine; I can log in but after that I installed AMD catalyst drivers for my graphics card. They are not working and even I opened the rc.local file as the root user 'sudo nano /etc/rc.local' copied and pasted the following lines just before the line exit 0 : 1) chown -R $USER:$USER /sys/kernel/debug 2) echo OFF > /sys/kernel/debug/vgaswitcheroo/switch it doesn't work for me. Every (HowTos)