When turning on my computer, the fans used to run full speed for a second and then back off to the proper speed which they run at for the rest of the time the computer is on. I recently tried to install a new motherboard that is very similar and when I put it in, the fans run full speed and are obnoxiously loud. I also smelled a bad smell coming from the power supply. XP wouldn't boot (but the BIOS loads) so I put the old motherboard back in. The fans still run wildly even with the old motherboard back in. Could something have gone bad in my power supply causing it to put out more power? Could this make my computer run up the electric bill? Are the fan speeds controlled automatically by the motherboards? I don't think the BIOS will let me change the fan speed manually. Any insight will be appreciated.
If your fans were connected to the motherboard, then check your fan settings in the BIOS. In default mode fans connected to the motherboard run at full speed. That's why they ran at full speed when you installed the new motherboard and later when you reinstalled the old motherboard. If you want the fans to be monitored and controlled, you have to change settings in BIOS.
If your fans were connected to the power supply, then you will have to borrow a good power supply from a friend and temporarily install it to see what happens.