Help fix corrupt GRUB

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http://unix.stackexchange.com – I have multiple partitions on the hard drive of my laptop (1 Crunchbang/Debian, 1 Windows, 1 Windows Recovery), I booted on the "recovery" partition for the first time and the graphics were completely wrong. I manage to find a way to reboot, and ever since, every time I try to boot, GRUB keeps crashing and my PC goes in a "launch/crash/launch/crash" loop. I had no problem booting on a Live CD though, and mounting the file system correctly. So I'm fairly sure it's simply a bootloader issue. What's the way to proceed now? How do I diagnose the issue? Can I avoid an unnecessary reinstall of (HowTos)