Originally Posted by sajjad_ss
but want windows xp bootable usb
Wasn't your original request installing Windows 7 in the Macbook?
From your situation you want to install the Windows operating system in your Macbook Pro. There are 2 ways to go through:
1. Install through BootCamp Assistance will let you install Windows on a separate partition, so your OSX and Windows don't run in parallel. You push the option key when booting the Mac to get into Windows.
2. Install through VirtualBox will let you install Windows into a virtual machine while youre running your OSX. The advantages of running parallel is that you can work with your OSX and Windows, though it does bottleneck your resources when running in parallel, if you prefer to utilise the resources on Windows then run it through BootCamp.
Windows disk should be bootable on default regardless. Custom booting will enable more features like install extra software and what not unattendedly.