please help me on my pc

i have a 32 bit win7 installed in my computer, i want to reiistall it a 64 bit win 7 using my bootable usb .but the problem is my bios my bios cant detect the usb bootable .

here is my spec and i believe my pc can handle 64 bit

mother board: emaxx mcp61d3 i-cafe socket am3 ddr3
processor: amd athlon II x2 250 3.0 ghz
memory: Kingston 4gb ddr3 1333
video card: 1 month old with receipt his redeon 6570 2gb 128bit ddr3
hardisk: 320gb western digital caviar blue
 
@romirez
@optimus
@frogger

my bios can read it now. but the problem is when it says press any key to boot usb....
i press spacebar and then restarts then load the 32 bit (original bit). when i reach starting windows and then desktop... im waiting to appear the win7 64bit installation but its not appearing i waited 5 mins and nothing happens .. i did it 3 times reboot , the results were the same