Force applications to quit, using extreme prejudice if necessary. It appears that XP can not do this.
I have just lost five minutes of my dwindling life, which felt of course like half an hour, because Internet Exploder 7 took 400MB of memory and then froze, and refused to be immediately killed. During this time I couldn't switch to anything else, "else" being the database that I was just having to rebuild, thankfully not before I had put more than 7 entries into it.
Luckily, I get to go home soon.