after a glance I recon that a thorough cleaning of the PC would be better than the usual dust blow with compressed air... one detail that caught my attention is the thick dirt that has built up around the heatsink of the CPU.
This is the very heart of the computer... can I leave the thing as it is, for what's infesting the precious component has nothing left of normal dust? Ok, let's proceed.
After unplugging the fan power connector, I disengage the ritention levers, separate the base, ... grab the heatsink and though slightly marveled in meeting some resistance, I pull to lift it.
Dismay! where the hell the microprocessor go? there's just an empty socket down there...
For some reason, the CPU remained attached to the heatsink and I've extracted it from the socket with the security level still down. And while I'm trying to detach the unfaithful chip seamlessly united with the plate, just while asking myself how on earth this could even be possible... my beloved Pentium 4, trusted companion of uncountable hours of computational torment and delight, suddenly comes off and falls, clashing on the memory banks. Impotent I witness the scene, like in slow motion, and as Murphy's Law predicts on the side where the pins are.
I lack the courage to watch... the horror! some of the pins (my sight has just lowered and I can't be more precise) had bent in the impact. The CPU won't fit in the socket no more.
How did this story end? Quite well! Thanks to my proverbial watchmaker precision I straightened the bent pins with my nails and re-assembled everything. and it works!
remember this lesson, kids. Sleep tight!