Since Apple was one of the first companies to eliminate DVD players from their computers, many manufacturers have sooner or later decided to do the same to try to reduce the size of their laptops as much as possible. Since Apple stopped using these optical drives in their computers, any user of the company's laptops has had to use a pendrive to be able to install each new version of the operating system that the company releases every year, an operating system that, unlike Windows, has been completely free for several versions.
Fortunately OS X is not the only operating system that can be installed via a USB drive, since Microsoft also allows this option after the arrival of notebooks, those notebooks with a very limited processor of approximately 10 inches and that did not include an optical drive. In order to install our version of Windows 7 from a USB drive, first of all we have to download or create an image of the DVD with the operating system to later transfer it to a USB drive to be able to start our laptop or PC from that drive and proceed to installation.
Once we have prepared our USB with the Windows 7 image or through the DVD, we will proceed to restart our device and go to the BIOS. Each computer offers us a different way to access it. To do this, we will have to press the ESC key, or the F2 key, although as I have said, as soon as we start the computer, it will show us how to access it before it starts to load the operating system. Once inside the BIOS we just have to go to the boot section (BOOT) and modify the primary boot drive to be the USB drive instead of the hard disk or optical drive that we have in our PC.