I thought the best way to proceed was to boot up using a Knoppix live cd in text mode, delete the existing partions 1, 2 and 4 and add new partitions 1,2 and 4 with the same filesystems as the original partitions had had before. I did that using fdisk and was told I'd have to reboot before my changes took effect. I did that and then tried to run fsck /dev/hda1.
Removing and recreating the partitions with fdisk doesn't actually format the partitions. Because you recreated them the same, you effectively made no change at all. The existing filesystems, with their errors, are still there.
How do I obliterate everything on hda but hda3 and create my other partitions and filesystems afresh, in a way that puts an end to existing filesystem errors?
use mkfs to create a new filesystem, eg: mkfs -t ext3 /dev/hda1 Repeat for all the partitions you want to format, and use the filesystem you want to use (probably ext3). This will remove everything from the partitions, and you'll need to reinstall everything again after doing this. However, if it's an old laptop and you were getting fs errors on all partitions, it's very possible you have a dying disk. Good luck :)