Thanks grogrecker and all others for giving remarkable support.
Problem has been identified. It was caused of corruption windows7 ISO source. WHen i tried to install Windows 7 on my 220 GB Harddisk, it was successfully installed each time but when i tried to make usb bootable from old Windows7 ISO then it was creating problem as i displayed in above snip.
Now USB has been successfully booted by fresh WIndows7 ISO.