My computer is back from its shutdown

It seems to work just fine.  And it didn't cost a dime to fix (other than a drive to Minneapolis.)  I was looking at a $425 fix which is enough money to wonder if a four-year-old computer was worth repairing.  Turns out the video card was shutting down—as designed—because it was overheating.  These iMacs are so nice because they can run without a fan BUT that means the air passages must operate like new.  Mine had gotten dusty—I figure I was losing 40% of my intake air flow.  So on a suggestion from MicroCenter's tech support, I cleaned the air vents, lowered the brightness of the display, and simplified my desktop.  This afternoon, I ran a full-screen hi-def .mkv movie for around 90 minutes.  A week ago, this very operation shut down my computer abruptly after 25 minutes with a need for a hard reboot to get started again.

These problems surfaced when I upgraded my OS to 10.8.5.  My iMac now has this program called Dictation—it was the reason I was willing to try another OS (I started installing new OS at system 6—nine systems upgrades ago).  It is a voice to text program that reportedly works well (the learning curve starts today).  It is a desktop version of the iPhone's ever popular Siri which several friends just swear by.  It works mostly because the major processing activity takes place at some big-brother Apple computer—I'd worry about privacy issues but when it comes to my writing, that horse left the barn many years ago.  We will see.  As someone who never learned touch-typing, just getting text written out is more work than it should be.  On the other hand, organizing my thoughts verbally is quite a different skill than the way I write.  It would be nice if I can make this work.