we don't even know if his mobo can be upgraded. or what os he uses. a ssd would be pointless on a 32bit xp system.
judging from the specs he gave the ram probably is DDR2 and if the ram is DDR2 then there is a fair possibility that his mobo supports sata 2 so SSD will be a nice upgrade. Also why do you think the SSD will be useless? Even if he has sata 1 it will boost the speeds significantly.