i cant seem to find AMD's CPU chart. but from my calculations
1670Mhz / 133.3333.... = 12.5 so tell your friend set his xp2000 for
133Mhz CPU external frequency: 133Mhz
CPU frequency multiple: 12.5
to OC xp2500 to xp3200 set your CPU external frequency to 200Mhz. leave your CPU frequency multiple at default which is 11. your result is 2.2Ghz. play a game for a few minutes, if unstable set CPU frequency multiple down to 10.5