a user reports that her mouse is not responding. Trying a different mouse does not fix the problem. what portion of the motherboards chipset is most likely causing the problem and why.

The southbridge chipset.

Explanation:

New motherboards or mobos has two types of chipsets known as: northbridge chips and southbridge chips. The northbridge chips are located at the upper part of the motherboard and perform major functions of the CPU. It is normally connected to CPU and works mostly with RAMs, memories AGPs etc. While southbridge are the lower part of the motherboard and mostly associated with the function of peripheral hardware like USBs and PCI slots devices including keyboard and mouse. Southbridge is also responsible for the function of audio, networking and others.

The reason why this problem occurs is probably a defective port (USB) or a software problem through motherboard drivers. To resolve this, you can re install the motherboard drivers or have the hardware fixed.