you don't have to go through all that. make a .txt file with 1 character in it so it isn't 0 bytes, then copy it to the drive. when you look at properties it will have a "size on disk" which you will find is the allocation unit size, because that's the smallest amount it can occupy.
Use the fsutil command:
You'll have to run this command with administrator privileges.
Now that powershell has caught up and has fledged out a little bit you can run this code in a powershell window:
Get-Volume | Format-List AllocationUnitSize, FileSystemLabel
you don't have to go through all that. make a .txt file with 1 character in it so it isn't 0 bytes, then copy it to the drive. when you look at properties it will have a "size on disk" which you will find is the allocation unit size, because that's the smallest amount it can occupy.