Hello,
I have an IBM 300GL PC- an old Pentium III-600 mhz, c.2001 vintage.
Recently, I opened the case to clean out the dustbunnies with a
compressed air cannister. When I set it back up again, at first it
wouldn't turn on. Then, a minute or so after pushing the power button,
it came on- but only the power supply fan and CD-ROM drive showed
activity, and a few beeps from the speaker. The hard drive was quiet,
the fan on the front grille remained still, and the screen remained
completely blank. And it wouldn't turn off by pushing the power button
for 10 secs, like normal- had to pull the plug out.

Does this indicate what the problem might be? And what might have
caused it?

I didn't touch the motherboard or any other circuitry when I was
inside. I did remove the front grille, and inadvertantly jostled the
PC a bit in the process. I also unsnapped the front grille fan to get a
better shot at cleaning it. When I sprayed the power supply fan, I
held it still with a plastic fork- but it works. I've checked to see if
everything is properly seated- it seems to be, but I suppose to be sure
I'd have to start detaching stuff and putting it back in.

Also, a friend of mine installed some new RAM in it the day before
this- but it started up fine after that, so I assume, unless he caused
some static damage that didn't show up until later, that that went okay.