Motherboard Overheating

Please give a detailed information about your system?

CPU DualCore Intel Pentium D 945, 3417 MHz (17 x 201)

Motherboard Name Gigabyte GA-945P-S3 v1 (3 PCI, 3 PCI-E x1, 1 PCI-E x16, 4 DDR2 DIMM, Audio, Gigabit LAN)

Motherboard Chips -Intel Lakeport i945P

Ram - 2x 1 GB DDR2-667 DDR2 SDRAM (5-5-5-15 @ 333 MHz) (4-4-4-12 @ 266 MHz) (3-3-3-9 @ 200 MHz)

GPU NVIDIA GeForce 7600 GS (256 MB)

PSU is 500w

Which brand psu?
If you have a local brand psu then definitely the main reason is your psu because it might not working efficiently to provide full support to the system components.

Try changing your psu with the psus of corsair,seasonic,cool master for best performance regarding psu.

Please re-insert your components again and make sure that their is no dust on the vents , gpu, cpu cooler and motherboard components as well.Because sometimes improper contact with the components part lead to this problem.