All major desktop operating systems have tools for making bootable flash drives, and whether you use graphical user interface or command-line tools, the process is straightforward and involves only a few steps. The dd program included with most Linux distributions automatically partitions and formats a USB drive and copies a disk image to the partition, leaving the unused space available for storage. GUI software in Linux and Windows performs the same task with a helpful wizard to walk you through the steps.
Windows Boot Drive Creation Tools
Use the Windows 8.1 Setup utility to download Windows 8.1 and create a bootable flash drive from the ISO file (link in Resources). The utility requires 1.8GB of free space for 32-bit Windows and 2.3GB for 64-bit Windows. Launch the setup utility and follow the on-screen instructions to download Windows and make a boot drive, entering your product key when prompted. Without a product key, you can't use the Windows 8.1 Setup utility to make a bootable Windows 8.1 flash drive. Use the product key that came with a Windows 8.1 installation DVD or purchase a new product key from the Microsoft Store (link in Resources).
Linux GUI and Command-Line Tools
The quickest way to make a bootable flash drive in Linux is to open a terminal window and enter the following command:
sudo dd if=/home/username/Downloads/ubuntu.iso of=/dev/sdb
Substitute the path to your ISO file for "/home/username/Downloads/ubuntu.iso" in the example, and substitute your USB drive's block ID for "/dev/sdb" in the example. Don't append a partition number to the block ID -- such as /dev/sdb1 -- because dd creates a new partition. Alternatively, use a GUI program such as Startup Disk Creator, included with Ubuntu, or UNetbootin, available in the Ubuntu repositories or from the developers' website (link in Resources). As with the Windows 8.1 Setup utility, these programs walk you through selecting input and output files and creating a boot drive.