I want to setup a bootable USB drive for Windows7. As I read from tutorials everywhere, I need at least a 4GB drive to store the setup files. The problem is I don't have a single 4GB drive. I have two 2GB drives. Is there a way to make these two drives together become bootable?
No, there isn't. Because once you used the first, it has to have enough of the OS loaded to provide driver to load the second. There are ways to slipstream Windows to have a smaller footprint, but in your case, I recommend getting a bigger USB drive/SD card - it's < $10 now.