Kubuntu saved my life. I was playing with the partitions on my laptop hd. I first used gparted, but as it didn't want to move to start of an extended partition to the right, I rebooted on a partition magic 8 cd. It asked me to convert the partition to extendedX, and I said no, as I didn't know what an extendedX partition was.

It proposed me to convert my /dev/sda5 to a primary partition, so I did it... reboot... and BANG, grub error 17. Reminded me of lilo old times when you forgot to run lilo after compiling your fresh new kernel. My "/boot/grub" was on /dev/sda5 at this time, and I forgot about it. Starting to panic, I don't have any rescue cd around. Grabbed my keys, 10min car drive & I had a kubuntu 7.10 cd rom, as one was available with "planete linux".

Boot kubuntu, sudo -s, mkdir sda3, mount /dev/sda3 sda3, chroot sda3, cd /boot/grub, grub --device-map=device.map, root (hd0,2), setup (hd0). My system is now up & running again.