While performing some disk operations, I just lost the Ubuntu 12.04 ISO image. Fortunately I had extracted the image contents to my thumb drive to install it through USB. But, my computer refused to boot from USB. So instead of downloading again I thought I would reconstruct the ISO image from the files extracted to my thumb drive. This requires boot information (which I have lost).
So please help me with the boot information (*.img or *.bif) and also the things that I need to take care while reconstructing the ISO.
Note: I am on Windows XP right now and I use PowerISO to create ISO image.