Create 64 w7 thumb for a 64 pc but preparing on a 32 system need help

i have a newly built pc i am trying to install windows 7 onto and the pc doesent have a dvd drive so i was gonna make a thumb to install windows 7 through

the new pc i built is using AMD 64-bit ,, i got a 64-bit version of windows 7 ,, i extracted the bootsector.exe and was going to use cmd to update thumb boot code so i can run it on my 64-bit pc ,, problem is that the only working pc i have available to create the boot-able thumb is a 32-bit system and when i hit enter with '>bootsect /et60 x: ' it tells me access denied , and displays ' bootsect.exe is not a valid win 32 application'

i need some way to just be able for my 32-bit system to update the thumb drive with the 64-bit bootsector file so i can transfer the win7 files and install it to my 64-bit system