Sometimes, older drives (by older I mean used, not antics) get corrupted and have to be repaired with some disk utility. Ether windows works or linux works, but both won't work. I've had this happen before. My only remidy was to work the disk over with some disk tool, often times using several before the problem was fixed, but in the prosess all data was lost from the drive.
That error 18 is usually gotten when you try and load a system beyond the limits of your Bios. I have a box that won't boot partition past about 80gb and and using 160gb drive. The work around for this is partition a /boot partiton on the front of the drive (hda1 or hda2 if you have windoz), within your bios limits.