Will a ATX processor fit in a BTX motherboard?

Reason I ask is I notice that a BTX processor cost nearly 30 dollars more then an ATX processor that"s the samething.

Is it because there is less BTX processors out there as of now and the heatsink setup cost a little more to make the the atx heatsink setup that comes in these retail boxes?

AMD Athlon 64 X2 4400+ OC 2.7ghz
2GB Dual Channel DDR 3200
Nvidia 7800GT
SATA II 2x 200gig 7200rpm 16mb cache RAID-0
Gigabyte Nforce 4 SLI

Processors aren't classified as AT/ATX/BTX. Their compatibility lies in the socket that they use. For example, a socket 939 Athlon 64 X2 4400 will fit in any motherboard that has a 939-pin socket, no matter if it's ATX or BTX.

Yes but intel does on their boxes, even though it's the same lga 775 they classify their boxes and the BTX box is shapped diff then the atx.

AMD Athlon 64 X2 4400+ OC 2.7ghz
2GB Dual Channel DDR 3200
Nvidia 7800GT
SATA II 2x 200gig 7200rpm 16mb cache RAID-0
Gigabyte Nforce 4 SLI

It's probably because of the cooler and the way it's mounted. I'm 110% sure that The processor itself will work in an ATX board. You'll just need to make sure the cooler fits and/or buy a cooler that does fit.