I recently had the need to rescue a laptop that had no rescue disk. The MBR was messed up. Fairly easy to fix (not the subject of this article), if you can boot from the original installation DVD.
Having an MSDN subscription I downloaded the ISO, but the computer did NOT have a CD/DVD device, just USB ports. I did have an 8GB empty (or one with discardable contents) thumb drive, but was not sure how best to copy the ISO to it so it was bootable.
At first I found a Windows tool called the "Windows 7 USB download tool", which probably would have done the trick. But further research showed there is an awesomely simple, free tool out there to do the trick. Go to https://rufus.ie and download it if you ever need it. I ran the program, inserted the thumb drive, and pointed it to the ISO image I wanted to burn. All the input fields were properly selected (it selected MBR partition scheme, Target sytem UEFI, FAT32 file system, and I left the default cluster size alone). Click to go and soon you'll have a bootable thumb drive.