There are three reasons to upgrade a motherboard:
1. The existing one has failed
2. You want increase your PC performance
3. To modernize your system
However, this is not the easiest of tasks as it can mean literally stripping the system down to gain access to the board, and then rebuilding it. Also, because so many other parts are involved, the potential for something going wrong as a result is higher than with any other type of upgrade.
These are two good reasons to not do it unless absolutely necessary. Another is that a motherboard upgrade may require other components to be upgraded as well.
The older your system, the more likely this is. Old computers will be incompatible with modern motherboards in virtually every respect. Even the case may need replacing. In this situation, a brand new PC makes more sense than a motherboard upgrade.
With systems between 3 and 5 years old, the CPU and memory will almost certainly have to be replaced. The good news is however, that the new motherboard will come with integrated networking card, integrated sound card, integrated VGA/HDMI ports.
A motherboard upgrade to accommodate a modern CPU could mean a new power supply unit as well. This is due to the high power requirements of these devices. It would be absolute silly to run one of the latest CPUs on an old 300 watt PSU.
The bottom line then, is that before you do it be sure that there is no alternative. Clearly, if the existing board has failed, its a no-brainer. If it’s a faster PC you want, try a memory upgrade first. If that’s not enough either, consider upgrading the hard drive to Solid State Disk. These newer hard drives are so much faster that it will greatly improve booting time, opening your heavy programs and your web browsing will be much snappier.