I went ahead with QTParted anyway and deleted the partitions, reformatting as ext3.

Installed Knoppix, which took a long time, and there were lots of hangs. The verbose text reported a large number of "Input/Output Errors" as it did this, but the install finally finished (more than I can say for either Mandrake or Redhat!). I rebooted to find Lilo (disappointed, as I have more faith in GRUB) and on Linux boot, a huge number of I/O errors

Example:
hda2: bad access: block=64, count=2
end_request: I/O error, dev 03:02 (hda), sector 64
isofs_read_super: bread failed, dev-03:02, iso_blknum_16, block=32

and finally:

FAT: unable to read boot sector
umount: devfs: not mounted
pivot_root: No such file or directory
/sbin/init: 418: cannot open dev/console: No such file
Kernel panic: Attempted to kill init!

Here's where the boot stops dead, and I am tempted to call in the police and report attempted murder. Poor init!

Very depressing. This is the third or fourth Linux distribution that has failed to install on this machine. Any suggestions?

This is a popular machine, and quite new: Toshiba Satellite 1405-s151, running Windows XP