Well ! Karmic Koala is using GRUB2 instead of GRUB.
Boot up from Karmic Koala LiveCD, open Terminal and execute this
Code:
sudo mount /dev/sdb1 /mnt
sudo chroot /mnt
sudo grub-install /dev/sda
sudo grub-install --recheck /dev/sda
Press Ctrl+D.
Code:
sudo umount /dev/sdb1
Reboot machine.

In case it doesn't work, boot up from Windows OS installation CD and select Repair. Execute fixmbr command at its repair prompt. It will re-install Windows Boot Loader and Windows OS will boot up fine.