You can, but you would need to use another system to prep the flash drive.
Of couse that goes without saying
Optical drives are used for so many other things besides loading windows. Are you sure you want to cut ~$25, and have no optical drive? Of all the hardware in a PC, this seems like an odd area to try and cut.
To be honest, I don't think I ever used my drive for any other thing besides burning and I have other computers for that atm.
Can you name some of these tasks?