Wherever possible the drivers should be obtained from the PC manufacturer's website as many of their PCs require custom-made drivers available only from them. This is certainly true of the "big brand" names like Packard Bell, HP/Compaq, Sony, Gateway etc.
Drivers are also supplied by the motherboard manufacturer if the computer is not a well-known brand or has been built at home using a motherboard bought from a supplier. In these cases the motherboard is usually an unmodified model and doesn't require custom-made drivers. Your motherboard is an Asus P4S800-MX. The driver packages are here:
http://support.asus.com/download/download.aspx
When the page loads, select 'All' in the "select a category" bar on the left.
Now type P4S800-MX SE in the bar which says "Input Model to search"
Now click the 'search info' button.
Very shortly you should see your motherboard model name appear in blue in centre of screen. Click it.