You have a computer with four DDR2 memory slots and two 512 MB modules currently installed. What is the maximum additional RAM you can install without replacing existing modules, if the system has a 4 GB memory limitation?

The maximum additional RAM you can install in the system is determined by the total memory limitation and the current RAM configuration. In this case, the system has a 4 GB memory limitation and currently has two 512 MB modules installed.

To calculate the total existing RAM, you multiply the number of modules by their size: 2 modules x 512 MB = 1 GB. Since the system can support a maximum of 4 GB, the remaining available memory for additional RAM can be found by subtracting the current RAM from the total limit.

4 GB (maximum limit) - 1 GB (current installation) = 3 GB.

So, the maximum additional RAM that can be installed without replacing existing modules is indeed 3 GB, which fits within the constraints of the system's capacity while ensuring that existing modules are retained.