Holy McSmoke!!
Kudos to the combined intellect of Nemesis and Javora!
I busted my piggy bank, went over to MicroCenter after dindin, and sprung for a $5 can of compressed air (really, freon, but what's a few fluorinated hydrocarbons among ozone-dependent humans?). My wife found out I was heading out and so saddled me with a bunch of errands, and I got back later than I wanted to.
But, I still pulled out the 423,815.73 cables I had in the back of the computer and the one in the front, cleared off a spot on my desk, heaved the metal prism up on the clear spot, opened it and zapped the CPU fan/heatsink and the other case fans, along with those in the PSU with the vacuum cleaner's hose nozzle near the blasting spots.
But, I still found a few points even the compressed gas, with the fine spray tube attached no less, couldn't reach. So I decided to do the reverse: I got some duct tape, and taped a drinking straw to the vac's nozzle and stuck it into those tight unblastable spots. Son of a gun, it sucked out the dust bunny remnants that clung tenaciously to those corners of the heatsink under the fan, those areas of the fans blocked from direct air blasting by the fan blades, etc. (Even so, little dust clumps flew everywhere almost inside my case; fortunately, my wife's little "Shark" vac is so strong it sucked all the dust clumps quite a few inches away from the nozzle.)
Well, it's now perhaps over a half hour since I plugged all my cables back on and booted up. It started at 42C and now is only SIX DEGREES CELSIUS (about 11 degrees Fahrenheit for us Yanks) higher than when it booted!
Wow. I thought either a K-BB or those six doomsday cigars in the old SFC1 campaign were tough customers. Bah! Dust beats them all!
Again, thanks to all respondents, but chiefly Jav and Nem!
Edit:
I *should* add, though, that playing SFC (1, in this case) raises the CPU temp by another 4 C to 52 C. Last night, BC, (before cleaning), it set off the preprogrammed temperature alarm! As soon as I closed SFC, it went immediately back down to 49 C and right now (2 AM, continuousl yon since I first posted tonight, it's now 47/48 C!!)
Now I know what they REALLY mean when they say, "Ah, cool!"