I've read many terrible things about this particular computer model's overheat issues. In addition, all of the dozen or so reviews I've read mention that the motherboard fries with 6-12 months of use. One guy claimed to be on his fifth mobo in less than a year.
Having just refurbished one of these puppies for my brother to use as his office PC, I'm worried, even though there's not much dust in his office and there's plenty of room around the case in all directions. I want to permanently forestall these potential overheat issues. I'm supposing the best way to do this is by installing an additional fan. The main problem so far is...
... the s3120n's case is tiny.
It seems that the only location in which an additional fan could be installed is on the side below the CPU's fan. Even then, no fan larger than 50mm is going to fit, and even a 50mm is going to be a tight squeeze against one (currently empty) card slot. Thus, I'm considering a 40mm fan like the SilenX IXP-13-14 (20mm deep), mounted on the side and pushing into the case and onto the mobo's heat dissipator (or what appears to be the mobo's heat dissipator). This would be perpendicular to the PSU's intake/exhaust fans' flow (front to back) as well as the CPU's single fan (which pulls from the front).
I'm comfortable with computers' "guts", but I've never installed a case fan. I've found no guidance online on how to install a case fan when there's no special fan-mounting location on the case, as with this surreally tiny Slimline. My current trajectory is to get the fan and install/jerry-rig it on the side using the case's many tiny side-vent holes.
Here is an HP article and video that should give an idea of this case, its dimensions, and the relative locations of its internals.
My questions are general ones: Am I on the right track? How might you, my dear saving answerer, go about this? Thank you in advance for simply bearing with my long, detailed explanation.