Ummmm..... The 754 Pins Are All First-Generation Single-Core, Single Channel Only, So A Socket 754 CPU Will be Your ONLY Choice, There Are Also Socket 939s, They Are For The DDR Only Second Generation Single-Cores And First Generation Dual-Cores AMDs
HOWEVER All Sockets Since Have Been 940 Pins Not "750" (AM2, AM2+, AM3)
AM2 And AM2+ CPUs Will Work In AM2+ Slots (And USUALLY Vice-Versa But That Depends) Socket AM3 CPUs Will Work In Socket AM2+ Slots But Not The Original AM2 If I Am Not Mistaken, Also I Think There Are A Few AM3 Only CPUs But Im Not Entirely Sure