I want to completely erase my hard drive and start again,

I want to install both ubuntu (11.04) and Windows 7.

I have the iso for both.

Because I do not have any DVD's I want to do this using my only usb drive.

I do not want to have to install an OS from the flashdrive, then go into it and write the second OS to the flash drive, so

Is it possible to make a bootable flash drive that I can choose to install either windows or ubuntu?