We'd say to try the power supply next.

OK, I'll give it a shot. I just ordered a power supply from you. I'll keep you posted. Thanks!

Update:
After I ordered the power supply, the Tivo stopped booting up altogether. The green light on the front and the fan came on but the startup screen never appeared. I simply unplugged it and waited for the power supply to arrive.

It arrived today and I promptly replaced it. Upon hooking everything back up, I was excited to plug it in - but was disappointed to find the same result. The light and fan came on, but no startup. On a hunch, I hooked up component cables and ran them through my VCR (this TIVO is on an old TV and was outputting to the TV via coax). Through the component cables, I was able to see the splash screen with the TIVO logo saying "Your PTV is starting up. Please Wait."

I bet this was coming on with the old power supply, too. I just didn't see it because I wasn't getting it through the coax. It was only when I used component outputs that I saw this screen.

So, it now seems to me that my HD was probably fine all along (although I replaced it twice), and my power supply was probably fine all along.

I think I can replace everything I can. Sound like an IDE controller? Maybe it's time to just let it die.......

Actually, if you get the splash screen through composite A/V, then you probably just have a bad hard drive now, but you had both a bad drive and power supply to begin with.

If you have lifetime service on the unit, I'd say it's worth fixing.

I don't think it's the HD. I have two drives that up until a week ago were functioning fine except the Tivo was rebooting. No matter which of those two I install, I get the same splash screen. I have one more HD I can try (the original 14 hour one that came in the Tivo) but I expect to get the same result from it. I think the likelihood of it being the drive is slim. I haven't replaced the ribbon cable to the drive. Maybe I'll give that a shot when I pop the original drive back in since it is easy. But, I find it unlikely that multiple drives (including one that I bought about two weeks ago) are dead.

Thoughts?

Let us what happens when you install a known working drive in the TiVo. IF that doesn't solve your problem, then you may have a bad motherboard on your TiVo, in which case you might consider a flat-fee repair:

http://www.weaknees.com/tff