Don't listen to him, Socket 939 is better for many reasons's, one being it can run dual channel memory, which is better than sinle chanel, but I wont get into that. It also is futureproof, you buy the socket 754 with an AMD 64 bit cpu, and that's what you will be stuck with, no future upgradeability like dual core.
Also, flashing means that you have to "flash the bios" with a certain file, 90nm amd 64 bit cpu's are fairly new and most of the motherboards haven't been released with the new bios to support it yet.
I have actually been thinking hard on this, which motherboard to get, I mean, I hear the MSI Neo Platinum or w/e it is called is a very nice motherboard; somewhere I heard that it comes with a working bios for 90nm.... If this is true or not, IDK. Here it is nonetheless- http://www.newegg.com/app/ViewProduc...130-468&depa=0