you need a 6th gen CPU with MMX, so at least a Pentium2 or K6 (i think still works?) - though it'll be very slow on anything less than P3 or Athlon... some simple games may run playable with LLE audio off.
edit: actually the FAQ says it runs on 5th gen (P1) systems but has anyone still got one to test? i think MMX is a requirement in the video plugin and possibly RSP now, can't remember.