These portable operating systems are so light you don’t even need to install them

You may think of operating systems as something you install once and leave on a hard drive. But not every OS needs to tie itself down to a machine. Portable operating systems are designed to run directly from a USB stick, external drive, or even a CD. They boot up quickly, don’t require installation, and often weigh in from a few megabytes up to a few hundred megabytes.