Overheating issues on Dell Optiplex GX620 Mini Tower Desktop

A few questions.
First, have you modified CPU cooling before, second, have you reversed front CPU fan (reverse air flow), third have you used pressurized air cans to clean you CPU heatsinks from dust, you can use vacuum cleaner as long as it doesn't touch any PC parts, and finally forth, which CPU heatsink you have, aluminum or copper, after cleaning flash the light inside and look for yellow parts inside.

O.K., I have not modified cooling system, I have reversed air flow and cleaned, and have not yet fried anything, and one is copper, the others are aluminum. They are all clean refurbs from Austin. My main question is how to find an aftermarket system to fit the skewed LGA775 socket. I have ordered several CoolerMasters that would not fit because they are square, these are skewed & returned them & looking for a solution to adapt.

When you reversed air flow, before overheat or after - this actually mean modifying Dell Optiplex cooling system. Unless you are ready to fry motherboard transistors you better turn you fans again. CPU fan must take air from outside and blow it inside, through the fins. There is a line of transistors called Mosfets, located between CPU socket and CPU fan, when air comes from outside into the case, Mosfets got cooled first, they are as important part of motherboard as CPU! If you reversed air, so CPU cooler fan working as exhaust, those poor Mosfets got hot air from processor, so they will fry soon, no joke!

Now, how PC with copper doing compare to aluminum? Same or much better? Also, have you removed any heatsinks already when you tried to mount retail ones? If yes, have you check how good the old thermal paste was, have you applied new one? And is it was good one, like Arctic Silver?

Now regarding CPU cooler. No, there is nothing out there to mount on those holes. What you can do is to buy extra fans and stick them inside to increase air flow (but air must move the proper way, from outside into CPU and next exhaust through the back panel).

I have very good information about this at home, I will find it and post, latest tomorrow. For now reverse airflow! You are cooking your Mosfets!

i mainly agree with kisianik, but with the gx620 it is a bit different. the system was manufactured incorrectly, most power supplies push air out the back of the pc. the power supply in the 620 was made to intake air from the back, at the same time front intake is pushing out back, so the power supply sucks in hot air. i monitored temps inside with oem config. internal air temp hit 120 within 20 minutes after boot and idle at desktop...

after reversing cpu airflow, internal temp does not exceed 95 inside under heavy load, and the fan is running more efficiently. if you still encounter heat issues, evercool came out with a fan that will fit the 3.5" floppy bay, and get a molex to usb adapter to power it. reversing the cpu fan does seem to help drastically, why dell decided to set this system up to intake hot exhaust air is beyond me but i looked for an answer to why reversing cpu fan helped and here is the answer

hope this helps...