I didn't want to give confederate false hopes. That system has bridge, memory, and cpu bottlenecks that'll nullify most of any HD improvements. Seek improvements are always nice, but I bet the transfer rate is already throttled by other system components.
Confederate, if the old drive is fragmented any new drive might appear quite a bit faster, at first. Download the
perfectdisk eval and see what it thinks.
Look for a 5400RPM handmedown. It might help a bit but don't expect wonders. Definitely don't bother buying a 7200RPM drive unless you plan on moving it to a newer laptop later.