"The third thing is - if I have the 270 mg HD hooked up, and I put the cd-rom on, it just sits there with the HD LED on."
hmmm. Let me know what you find out. I have a very similar problem with my A4KD. One CD drive refuses to allow the machine to boot up even though it works fine on another nearly identical Amiga A4K. I get the led light, blank screen, everything. Can you boot from a floppy?
