I recently changed my system to a dual-boot setup with Ubuntu GNU/Linux, and it worked magically for awhile. However, I was using Windows XP to make a FAT32 partition (seems like I had to make it in Windows for it to be recognized), when my GRUB boot loader messed up. I couldn’t boot my computer. Luckily, I had Ubuntu Live handy, and I booted into a live session.
I made a rescue floppy by going into GRUB’s folder (with stage1 and stage2), and running the following commands:
dd if=stage1 of=/dev/fd0 bs=512 count=1
dd if=stage2 of=/dev/fd0 bs=512 seek=1
I now had a bootable floppy. With the floppy, I can boot into the GRUB prompt. From there, I could either type in some commands to boot Linux, or I could install GRUB. I installed it by:
grub> root (hd1,0) or whatever partition Linux is on
grub> setup (hd0)
I now had GRUB back again!