After installing two memory modules, you power on the system to check for errors. You find that the BIOS program recognizes only one of the memory modules. What should you do first?

When you discover that the BIOS recognizes only one of the installed memory modules, the most appropriate first step is to ensure that both modules are seated properly in their slots. Inconsistent recognition of memory modules is commonly caused by improper installation. Memory modules need to be fully inserted into their respective slots and all the way down until they click into place.

If one module is not seated correctly, it may not connect with the motherboard's memory controller, resulting in the BIOS failing to detect it. Additionally, reseating the modules allows you to check for any visible debris or damage in the slots that might affect connectivity, thus addressing a potential installation issue before moving on to more complex troubleshooting steps, such as BIOS updates or module replacement.