Hi!

I've got a can of compressed air, but I'm wary of it.
Sometimes a damp kind of spray will come from it.

That's harmless, it's just the liquefied form of the difluoroethane
gas coming out. It usually happens when the can is tilted, held upside
down or is still fairly new. If it comes out as liquid, it evaporates
almost immediately and shouldn't cause problems unless you
deliberately dispense the liquid for a long time.

I stopped using those cans long ago, because I work on a lot of
computers. I bought an air compressor at a deep discount and haven't
regretted it for a minute. A few good "FOOFs!" later, and the dust
that was in a computer is unquestionably gone.

A ps2 model 90 - would that be a classic green text
on black screen look - I'd be quite happy if they'd
never evolved beyond that....

It's a nominally 486 era system made in the early 90s. Unofficially,
386 versions exist, made as a "special bid" system. I've seen exactly
one set up that way. Since the processor comes on a "complex card" you
can put any of a 386, 486 or Pentium 60/66/90 MHz CPU in it. Some
people have dared to crank the Pentium 90 version of the complex up to
accept a 233 MHz Pentium MMX CPU. That's on the outer fringes of
reliability, however.

I suppose it could have run "green screen" programs with a serial
terminal like the IBM 3151 attached, or by running a terminal
emulator. It would have been sold with any of PC-DOS, Windows 3.1x or
OS/2 when new. It can run up to Windows 98 with enough processor, disk
and memory resources installed.

Come to think of it, I've never seen a green monochrome VGA
monitor...paper white and amber (!!!!) VGA displays, yes.

William