A couple of nights ago, I replaced my ailing Tivo Series 1 hard drive with a brand new Samsung 80GB, which gives around 90 minutes of recording time. The old Quantum Fireball, while not entirely dead, was having obvious issues with writing to bad sectors.

I highly recommend Weaknees.com for your Tivo repairs/upgrades, although it's a tad bit expensive ($130 for an 80GB HD), it comes pre-formatted, and ready to go with the much-needed special-keyed Tivo Allen wrenches.