So I have an optiplex 960 and lately I dismantled all my pc and cleaned it thoroughly from the case, fans even to the front thermal sensor which is in front of the fan. The dust buildup on it was unbelievable as it wasn't cleaned for almost a decade. Now during these years I used it for gaming, not great performances but it was what it was and I was happy with it.

After mounting everything back in I noticed that for the past year ( since I changed the PSU ) I had placed it COMPLETLY wrong in the sense that I force screw it in place with some holes I made??? And the fan inside the psu on the side with the honeycomb shapes( where the air gets inside the PSU ) was placed towards the case wall this entire time, having only like 1 cm of space to breath.

After I fixed it and booted the system ( haven't had any problems even though the PSU was in the wrong direction) I noticed  the front fan which is facing in the heatsink ontop of the cpu was spinning normaly getting more air intake on the case as it was never cleaner until I started doing tasks like oppening browsers, oppening game launchers and even windows folders which made it spinning so fast I swear I thought it was gonna blow up, my table started shaking slightly and I put my hand infront of the fan and it was a breeze I've never felt on fans.

I remembered the processor didn't have much thermal paste if not at all except for some small bits here and there which were almost dried up but that wouldn't make the fans spinning so much because I checked with SpeedFan and CPU temperatures were great and my fans weren't even showing on SpeedFan so I couldn't limit their speed.

I also tried moving the thermal sensor abit because maybe It wasn't detecting normal airflow but still the same problem.

If anyone could help me it would be greaat!

Changing fans or buying thermal paste is a no-no in these times of quarantine so thanks in advance for everything