Ubuntu dual boot OS crashed my computer. Now my computer won't boot. Please Help

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http://askubuntu.com – I've just tried to install ubuntu 12.04 dual boot OS with Windows 7 and it finished installing in ubuntu. However, it said that the bootloader "grub.." failed to install. The same exact problem here I receive the error 'grub-install /dev/sda failed' while attempting to install Ubuntu as the computer's only OS. . When I tried to restart my computer, it went to the hp screen since my computer is a dv6 hp laptop and then it goes into this black screen with no words or any buttons will work. There is just a blinking underscore that seems like it'll allow me to type but makes error soun (HowTos)