A: Possibly

How much memory your Windows OS will recognize depends on which version of Windows you are running. 32-bit versions of Windows will see (and utilize) only 3GB or 3.5GB. To utilize more memory, install a 64-bit version of your OS. More information about OS memory maximums can be found at http://www.crucial.com/kb/answer.aspx?qid=4251.

A: DDR2 memory with support for DDR2 PC2-6400 speeds.

A: 2048MB.

Adding the maximum amount of memory will improve performance and help extend the useful life of your system as you run increasingly demanding software applications in the future.

A: No.

No, you can install modules one at a time, and you can mix different densities of modules in your computer. But if your computer supports dual-channel memory configurations, you should install in identical pairs (preferably in kits) for optimal performance.

A: No.

Your system does not support dual channel.

A: No.

Your system does not support ECC. Because ECC and non-ECC modules should not be mixed within a system, install the same type of modules that are already in your system.