Droopy, is the motherboard a GA-7
ZX? I couldn't find a 72X. According to
this list you aren't going to get much more from the board you have. But as fairly good motherboards can be bought for less than £40, you might want to investigate updating it too. But be careful! It's easy to get carried away going down this route when a new system would be cheaper and better.
Regards
Stoney