(Edit: After a nice debate with fellow techs , as you can read down below, The trick works great, but the reason why it works is what was at debate. The way I was taught on the reason why can not be confirmed or denied. But a good reason which can be confirm is listed below. I am always open to learning new things and even correcting things I think I already know :-) )
Regarding your friend, here is a good quote regarding this very issue from experts-exchange.com. Sorry it's subscription, so I can't post the direct link:
"If I want to do a "true" cold boot on an ATX computer, I always unplug the computer and wait at least 10 seconds. The fact is, even when you hit the off button to your computer (unless its AT based), you are still receiving 5+ volts to the motherboard and PS. True that your disks do spin down, but in a sense the computer is not 100% powered off."
So until you unplug (hitting the off switch on a power strip will do the same thing) your computer powersupply and motherboard will likely still be "on".
Therefore, if your motherboard is in some kind of error state (and anything integrated on it, or plugged into it, such as NICs, soundcard, video etc) the motherboard would not get fully reset with a simple shutdown.
I haven't been able to find anything that demonstrates mutated electrons *don't* cause computer crashes, but here's one of the few places that mentions them, which I don't think would happen anywhere near your computer:
I was trying to back up what you said. I haven't seen your trick in practice and it fixing something (other than routers and modems), but I've read plenty on the concept. Basically what you're saying (and what I tried to convey) is that you're method is the only way to etirely ensure all electricity has been purged. It comes down to draining the capicitors.
Now whether there are mutated electrons or just a confused piece or hardware or instruction (I guess like a stuck pixel in an LCD screen) I can't say with certainty. The point is as long as the computer is plugged in the PSU is receiving power. You could test this by plugging in a computer and using a multi meter and check various components.
The capicitors in a PSU and a CRT monitor hold enough juice (even "long after being turned off") to kill you. That is why they are considered field replaceable units and unless you are specifically trained in how to drain them and work on them you just replace it. That CompTIA A+ stuff for ya. :)
If I looked a little I could find a quote from Scott Mueller from his Upgrading and Repairing PC's (18th) edition, but I couldn't provide a link. Speaking of him you could always look through his forum...at http://forum.scottmueller.com
I think the both of you are right and it makes perfect sense.
When a piece of hardware is in a error state of some kind, or just not working right for that matter a reset is needed. As long as the system has power a true reset can not happen. Thus removing all power and draining it does the trick as now everything is cleared out. The hardware runs off of electricity and as long as it is getting it its not being reset. Now what causes this to happen is at this point (without some hard proof) unknown. I was told mutated electrons as this seem to happen a lot after power surges and such. But no matter the reason the point still stands. Draining the power is a good trick to know.
I will update the page shortly.
Original Page info:
Let me give you a true story, a customer of mine had 2 computer systems in there office. One morning they come in and one of the systems wont boot, it would freeze at the bios screen when checking memory (Think memory error? wrong) Then the 2nd system had been on all night and was acting strange, internet going horribly slow, network to a crawl, programs running slow, just crazy. So they reboot the computer and guess what it freezes during boot up also.They give me a call and are all panicked that both there systems went down over night. I told them don't worry I think I know what happened.
Here what's I told them to do. Go to both systems and pull the power cord out of the back of both of them. Now with both unplugged try to turn them on. This will drain the power that is left inside of them. Now plug them back in and turn them on. And both systems booted fine and they have been good to go. Well you might ask WTF? How did that have anything to do with it? The answer: Dirty Electricity. When you get a power surge or other form of power corruption the electrons can mutate. Now since the systems run off the power naturally they will be affected. This is also why so many tech support places for modems, routers and the like always have you unplug the unit for 60 sec or more, they are draining the power from the box. Believe it or not half the time the problems are fixed by simply resetting the power. So as a first step trick to trying to find out why a systems hardware seems to be going crazy on you out of no where, try this trick. So for you people out there that take your computer to a repair shop but once there your system is running fine, well now you have your answer.
Since the power was unplugged and got reset by the time its at the shop everything is working fine. So add this simple yet effective little trick under your tool belt.