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How do I install or upgrade an operating system without a CD or DVD drive?

Answer: For about ten years, CDs were the standard way to distribute operating systems. As the size of OSes grew, they no longer fit on CDs, so DVDs became the standard medium. This also lasted for about ten years.

Now many computers, especially laptops, do not include an optical drive. So how do you install an OS on a computer without a CD or DVD drive? You have two primary options: 1) download it, or 2) use a USB flash drive.

1. Download

Most major operating systems can now be downloaded directly from the software company. For example, you can download Windows 7 from Microsoft's website here:

Download Windows 7

When you manually download an operating system, it may be saved as a disk image (like an .ISO file). When you double-click it, the disk image will mount on your desktop as a CD or DVD. You can then install the OS just like you would from a physical disk.

If you are are already using Windows 7 or 8, you can download Windows 10 directly from Windows using the "Windows Update" feature. You won't need to worry about mounting a disk image because Windows will begin the installation process automatically.

If you are a Mac user, you can download the latest version of OS X from the Mac App Store. Simply open the "App Store" application (included in OS X 10.6 and later) and search for OS X. After you download the latest OS, it will automatically begin the installation process.

2. USB Flash Drive

If you don't have a fast Internet connection, downloading several gigabytes of data may not be a viable solution. Additionally, if you are installing an OS on a blank hard drive, you might not be able to use the download and upgrade method described above. In this case, using a USB flash drive might be your best option.

In some cases, you can purchase an operating system on a flash drive (such as Windows 10 and OS X Lion). Simply connect the drive to your computer's USB port and install the OS just like you would from a CD or DVD.

If the OS you want to install is not available for purchase on a flash drive, you can use a different system to copy a disk image of an installer disc to the flash drive, then install it on your computer. Just make sure that the license agreement of the software you are installing allows you to copy the data to a personal flash drive. If you are installing Windows, you will still need a valid license key to complete the installation process.

Published: March 24, 2016 — by Per Christensson

Answer from the PC Help Center