I suppose everyone but me already knows what to do about this annoying little problem: the power leads on a desktop computer constantly falling out whenever some heavier cable is nudged. They're so loose, and have been loose on every motherboard I've owned, that I suppose they were designed to be loose. I finally took to plugging them back in while the computer is turned on. Is that supposed to be dangerous? My experience suggests not: I can't say I have received any shocks; nor does the computer appear to be damaged.

If I'm right that it's not particularly dangerous, would this be how everyone else handles the problem? Just plugging the leads right back in?

No power leads or any leads really should be loose, at very least you stand a high risk of coruupting your data, get it sorted out if you cant do it youself take it to your local pc store and get the leads fixed.

Seems like you need to route the cables so they accidentally do not fall out. I assume you are referencing the header connectors which are fairly loose as compared to the Molex and SATA power connectors. The power and reset leads are just momentary push button switches, low voltage and current so there should not be a problem plugging them back into the header.

I have in the passed damaged a motherboard by hot plugging in the AT keyboard many many years ago.

Yes, the header connectors are what I meant. Used the wrong term again.

On those particular conncetors, it is usual to have externat or internal pull up resistor to V+. The second lead is ground, and it's difficult to blow anything except V+ with that.

Static can often be a thing, though. So you personally charge a pin just by holding it, and if it gets anywhere sensitive with a high impedance, watch out!

For me, it's a question of respect. If you respect your electronics, don't hot plug it and discover weird and wonderful ways of blowing it up. I know it's basically harmless but put that with another fault and you have the making of a lot of trouble.

What I think I would do is to bend the pins very slightly so that they grip the plug better.

There speaks a wise man.

Ideally bend them slightly away from each other, as nearly any other direction raises an issue.

I don't bend the pins. I use a jewelers pick to tighten the female connectors in the case cables. If that doesn't work (I've personally never seen that problem) a small bead of clear silicone caulk/adhesive on just the plastic housings (never on metal connections) can add resilience but still be easily removed with proper tools.

Just FTR silicone caulk is an insulator that can resist hundreds of volts, so a mere 12-24v maximum in most PCs is of no concern whatsoever.

For something like a valve base shrinking the female of the base is the way to go. You don't want to bend valve pins mounted in glass.

But you'll crack plastic and wreck things if you try anything on the female pins of these little 2.5mm (.01") spaced plugs under discussion. I'd expect 3.3V or 5V max. No glass in sight. Fatmac is on the ball.

Guess I've been either careful or lucky

Probably the former. Both you & I remember the days when labour was cheap, wages were poor and spare parts were #£@$&€%! expensive. When I got into televisions here, the average week's wages was <£50 and a 22"TV was £400. People used to buy them on hire purchase. Guys with a bad payments record couldn't buy, so they had to rent.

You were respectful of what you had.

Usually for best cooling you should have the covers on the chassis and if I am messing with the insides then power is off anyway. I try not to route the header cables around the drive or PSU cables so nudging isn't possible. Last time I messed with the insides was a few years ago when I changed a hard drive. I say it just being careful.