First, make absolutely sure you really have a hard drive problem. Twice I've had TiVo support insist my HD was bad and my only option to pay them to replace the whole unit.
Turns out, it wasn't the drive at all. In one case, another, non-TiVo, remote had one of its buttons depressed and was interferring with the TiVo remote signal, causing every command I gave to be repeated a hundred times or so (most annoying). I also had a rebooting freeze similar to yours during that episode.
The other case was just as dumb -- my Monster power center developed a bad outlet. The one my TiVo was plugged into. So the power would glitch and the TiVo would reboot itself. A lot. Also most annoying.
But neither would have been half as annoying as doing what TiVo suggested, only to find the problem still there with the replacement unit (especially since they would only replace my 200-hour AT&T with a 40-hour unit -- and wanted $150 for the privilege!).
So, before doing anything drastic, clear the room of all other remotes, check your power -- at both ends -- and look for anything else (somebody put a microwave nearby recently?) that could possibly be giving you trouble. As a last resort, before tossing the old drive, plug it into your computer and see if it still won't work.
Ain't technology grand?