With the retail package you'll get a 3 year warranty from the manufacturer and a HSF which is adequate as long as you don't plan to OC. With OEM you'll usually get a 15 or 30 day warranty and you'll have to buy a HSF, which offsets a lot of the difference in price between OEM and Retail.
My opinion is, go retail if you don't plan on OCing, go OEM and get a good HSF if you do want to OC.
"There's no such thing as gravity, the Earth just sucks"
the price difference between the the oem and retail P4 1.6A is almost negible (like $15 at best)...i would suggest just getting the retail because not only does it have a great HSF...the fan is hideously quiet...
<b><font color=red>ATI</font color=red>'s drivers are like a broken faucet, they both keep on leaking...</b>