P4 3.2GHZ or Athlon 64 3400+
the 3400+ is socket 754
personally I would go for a socket 939 3200+ or 3500+ (I game)
if I used it for mathematics or multimedia, I would choose the P4
Sorry for this noobish question, what's the difference between Retail and OEM? I know that you buy retails at stores and stuff, and OEM comes with your PC, why is there a price difference?
retail = normal way to buy, with warranty, proper box and stuff
OEM = cheaper, normally bought in bulk. usually doesn't have as big warranty, and often doesn't come with any "extras" like a HSF, or game CD's