grub issue while installing ubuntu

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http://askubuntu.com – First of all I am a non technical guy so it will be helpful if you can give step by step instructions. I have windows 7 64 bit and windows 8 32 bit. As suggested by one of my friends I installed wubi.exe and when I am trying to reboot the system there was an error" with couple of lines(grub-minimal bash line) is being displayed along with a blank "GRUB>". i don't know what to do further please help. (HowTos)