Dated comp is not a problem, I installed and ran on a 15 years old single core Pentium3. My feeling is, pFsense works good with generic, non-custom PC, and you did not volunteer what brand, if any, this dated PC is, and Mr. Obvious would want to now, if this PC a WORKING PULLED, meaning it was working perfectly right before you decided to install pFsense or it, or you just found something at the garage sale with unknown history?