GRUB not loading

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http://stackoverflow.com – I just installed Fedora 18 alongside a pre-existing windows 7 from a live-usb. created all necessary partitions as recommended: / :40GB /boot :200MB /home :350GB plus BIOS BOOT of 1MB The setup ended with a successful installation message but when I rebooted the GRUB didn't load. In fact the BIOS didn't show HDD in the boot order. When I again booted using live-usb I saw that all the partitions were existing. I tried reinstalling; the setup detected previous installation. I reinstalled with same partition sizes but again the boot failed. Is there anything that I might be missin (HowTos)