Silly story just happened 5 minutes ago.
I was working in a big Word document with (sigh) Word 2001. Big, but not big enough to crash my PowerBook. If a 1.25GHz with 1.5 GB of ram can't handle some tables and a pair of macros...
Setup: PB with a laptop stand, hooked to a 20" display and external keyboard and mice. Stereo system playing best music ever.
And the thing starts getting silly. I try to move a window and the system freezes. I say what the f*** this system from prehistory can't really handle iTunes, Word and Acrobat? Is pre-emptive multitasking really that good and necessary? Who will win the Champions League? Sorry, getting off topic here...
Try alt-cmd-esc and the Force Quit appears. But I can't do anything. Ten forced reboots later still the same thing. I try opening a different word document and after 3 minutes or so freezes.
On the 11th reboot I realize that the trackpad was working. I look at the bottom of my windows 2000 era good old Logitech mouse. The light was blinking awkwardly... AHA! I plug my magic mouse and well... USB overdrive doesn't like it but it's better than anything.
TL;dr: Mac OS 9 still can do two things at the same time. Old hardware can fail eventually.
Have a nice day.