Been having some intermittent freeze-ups on a S2 unit, which was upgraded with a Maxtor 160GB about 1.5 yrs ago. Today, the GSOD came and didn't go away after several hrs. Suspected the hard drive (I've had 3 maxtors die in the past 2 months in various equipment... go figure), and re-installed the original TIVO supplied Maxtor 40GB that I took out of the machine originally. With the new, old (e.g. original 40GB drive) installed, the Tivo booted, and things looked OK. It obviously needed to connect and get acquainted with the new software. Well, it connected via network, downloaded whatever it wanted, and went to reboot. Things seemed to be working before the download -- i.e. it found the network, and I could navigate menus. Didn't try to play out already recorded shows, but didn't sense anything was amiss with the unit with this "new" Hard Drive. On reboot, said there was a Hardware Error #51, and to restart the system again. Am continuing to get this error upon successive reboots. Before I attempt the pleasures of trying to navigate Tivo Tech Support, does anyone know what error 51 is? I'm attempting right now to clear off all the old recorded info; if that don't work, I'll retry guided setup. Any help appreciated.