Delete all the partition and create new one.
Try using cfdisk to create partitions.
After partition is created,reboot and run knoppix-installer.
Knoppix-installer will always reformat your hard disk.
The importnt part is creating partition.

If above doesn't work, try get other third party partition manager.
Or get ultimate boot cd, comes with plenty of tools :
http://www.ultimatebootcd.com/