Ok, so I got a new heatsink with a fan as a replacement to my old heatsink without a fan. My old heatsink used to make the CPU heat and then turn off unless I place a fan on top of it, so I used to place my case fan on top of my heatsink so that the CPU stays cool.
I placed my new heatsink, and now no need for an external fan to add on top of it, since the PC doesn't turn off. BUT now, all games throttle during playing, and when I touch the heatsink, its not that hot (It should be hot, since CPU heat is transfered to it)
When I placed the new heatsink, I haven't removed the CPU thermal paste (The thermal paste was a bit dry, as if you leave a toothpaste on the floor for weeks), and placed the new heatsink on top of it (Which had thermal paste under it), so now two thermal pastes were mixed, and some of the thermal pastes from both CPU and heatsink got removed, and there are like spots with less amount of thermal paste on the CPU, and its really messed up.
So my question is, does removing the thermal paste and adding a new one would fix the throttling issue? Or is it from the new heatsink/other issue?
Notice that the heatsink was placed correctly, and touches the CPU, and the fan of it is running, and its really really fast.
The motherboard is working fine, the GPU is working fine under a good tempreture, the power supply is working as it should be, and the problem is NOT from the power supply, since I tested the PSU on another computer, and it was working fine during games (Its a Corsair 550W).
I got an Intel Pentium 4 650 3.4 GHz , I know its somehow old, but thats not my main PC, and I just want it for home use (Web surfing, playing non-modern games, etc...).
Clean the old paste off the cooler and cpu , them reapply thermal paste , a pea sized dot at centre of CPU attach cooler and you're done . There are posts on removing old thermal paste , after doing all this things should be good .