Hands up! Now step away from the computer...

I've had this PII for like what, 7 years now? Works great, no problemo. I don't tinkle with it, I don't buy new components, just threw in a CD writer extra RAM and then just let it be. It’s old and wheezes a little bit, but still keeps on chugging along just fine.
But guys? Nooooooo. You're always upgrading something or other. Off fixin' some part that is clearly not broken, or just opening it up for the hell of it. You all think you were born mechanics or electrical engineers.

Case in point, my kid brother has had my computer for all of 4 days, but then yesterday he calls to tell me that out of the blue it just went ‘poof’ and died.

It went poof?
Uh-huh.
What do you mean it went poof?
Huh? That’s the sound it made. I was trying to replace the fan unit.
And this is because....?
I was trying to fix the wheezing.
Gee, thanks. You sure fixed it alright. Consider yourself banned from the vicinity of my PC. Twat.

*edited to add:*
I apologise for my abuse of the word 'just' in those first two paragraphs. I'm just hungry.