Hi Victor, I don't have a lot of experience with FreeNAS, so take my ideas with a grain of salt. Well more salt than just a grain. I looked up your computer on the hp.com website. The front of the case looks nicer than the really old HP desktop systems. You have a P5LP-LE motherboard made by Asus, and that has only 4 SATA connectors on it and just one PCI Express x16 connector. That motherboard can only take a maximum of 4 Gb of memory. DDR2 memory is more expensive than today's DDR3. If you have a Core 2 Duo, it is 64 bit capable which is good. You you might be able to upgrade that to the Core 2 Duo E6850 for a low price. Overall, if you can upgrade your memory to 4 Gb cheaply, it might be worth trying. With all that said, let me stress that I am just starting to use FreeNAS -- but on a newer motherboard, the MSI 890GXM-G65, and with a 6 core processor that is showing it's age by today's standards. What do I really know? If you do decide to give things a shot with this motherboard, please let me know how it works out for you. I'm extremely interested in your project.
Bob