He won't notice a difference with that small of an upgrade. I can't feel the difference between an Athlon XP 1700+ and a 2500+ outside of games, and that's a much larger difference. I can feel a difference between a Duron 800MHz CPU and a 1700+ though. If he really wants to see a difference, throw in an A64 2800+, or if you really don't want to spend more than $45, you could probably pick an ECS K7S5A and an Athlon XP for about that price in the For Sale forums (maybe $10-$15 more). That might make a noticeable improvement in general performance.