The most likely reason that the system is not utilizing all the available RAM is that it is running a 32-bit OS. A 32-bit OS can only address up to 4GB of RAM, and some of that is reserved for hardware and system use1. Therefore, even if the technician installed 8GB of RAM, the system can only use around 3.5GB of usable RAM. To use the full 8GB of RAM, the technician would need to install a 64-bit OS, which can address much more memory2. The system missing updates, the system's memory failing, or the system requiring BIOS updates are not likely to cause this issue.