Open up Command Prompt
You can do the first step within a normal command prompt window or within the WAIK Deployment Tools Command Prompt Window.
This launches the DiskPart program which is included within Windows Vista x32, x64 and Windows 7 x32, x64.
Before you do anything you will want to see which disk is which on your computer.
select disk 1
You will want to pick the corresponding disk in which you want to use for your bootable flash drive. Careful, because this will completely erase the disk you select.
This cleans up your disk.
create partition primary
This creates the partition on your flash drive.
select partition 1
This selects the partition you just created in Step #6.
This marks the select partition as active.
format fs=fat32 quick
This will format your flash drive in FAT32 format. Make sure you use the quick command otherwise it will do a standard format and will take a while. For bootable flash drives the quick format will always be fine. You can also add the NTFS switch instead of the fat32 switch.
This will assign the next available drive letter to your flash drive. (You can also specify which drive letter you would like it to be assigned)
This exits DiskPart.
This exits CMD.