A pen drive is more than just portable storage; it can significantly extend the utility of an older PC.

The Last Install

You install a lightweight version of Windows 7 onto a high-speed USB 3.0 pen drive. When you plug this drive into any PC and boot from it, you are greeted by your own personal Windows 7 desktop, files, and applications.

If you need to install a fresh copy of Windows 7, you cannot simply copy the files from a disc to the USB drive. The drive must be made "bootable" so the computer knows to look for it upon startup.