Well that's what happens when you install something that was never meant to be on the hdd. Go here: http://kanotix.com/files/ get the 'fix-all' script and run it. Hopefully that does the trick. Then once you get booted in Linux maybe do

apt-get install grub
grub-install /dev/hda
update-grub

Then you *should* be able to boot either OS (and I use the term OS loosely when referring to anything from Redmond) :P