I followed those instructions, using
dd if=/dev/hdb1 of=linux.bin bs=512 count=1
I copied the linux.bin file. It was 512 bytes as expected but if I open it with a text editor it seems that it's just full of spaces, there are no strange characters like I'd expect.
If I start my computer and select linux from the boot list, the computer seems to get stuck, displaying a flashing underscore in the top left corner like it's trying to load something but can't.
I don't see what I'm doing wrong, and I'm pretty sure the created linux.bin file isn't supposed to be empty.