Over the years my MBP has gotten slower, and the various tweaks I have read online haven't really helped. But the past couple of months it has suddenly gotten *ridiculously* slower -- beach ball all the time, keyboard not responsive, having to Force Quit frequently, even having to press the Off switch and turn back on frequently, when I can't get Force Quit to respond. Last week something happened which I'd never seen before: a message appeared telling me in several different languages that I needed to press the Off switch, then behind the message the screen slowly darkened from top to bottom like a curtain descending. I have 10 free MB. (I know that people recommend more, but it's been 10 free for a really long time and the extreme behavior only started recently.) This week I happened to check the amount of free space on the HD when a huge slowdown happened, and discovered that it said only 1.5MB free -- which I knew couldn't be right. I rebooted, and once again there were 10MB free. I eventually discovered that after running Safari (5.1.7) for a while (less than 30 minutes), the HD once again reported only 1.5MB free. So now I'm having to reboot every half hour or less. I haven't seen this behavior with any other program. Is this known behavior from Safari? Back when the MBP was only starting to run slowly, I never checked the HD space so frequently, so I don't know whether Safari was eating HD space back then or not. Is there possibly some Safari preference I should set differently? I've cleaned the cache, but that doesn't cause any major change in the HD space.