What happened? Are you another victim of the Update Problem? Or is it something else?

After three years of mostly faithful service, the machine just seems to have died—it will turn on, but the screen fades up into unpleasant bluish-white striations, like a sort of Plaid of Doom, from which my computer proper is inaccessible. It can be made into a target drive, but will not even sustain this mode for more than about an hour before it freezes up (or, since the problem seems related to overheating, melts down) again. I am annoyed. My old computer lasted me all the way through Brandeis. This one could at least have made a stab at grad school.