How to Add a Second Operating System to Your Computer

by J.E. Myers

Installing a second Operating System (OS) on a computer is called "dual booting" in the computer trade. Dual booting provides an opportunity to try out a new OS, like Windows 7 or Linux, and yet still have access to a trusty favorite like Windows XP or Vista. The key to setting up a dual-booting system is the correct partitioning of your hard drive.

How To Add A Second Operating System To Your Computer

Evaluate your hard drive space. For example, if you want to dual boot XP and Win7, you'll need a minimum of 21GB of free space just for the OS installations, according to Microsoft. If your hard drive is under 80GB, upgrade to a larger size. Move everything from your old hard drive to the new drive using a product like Acronis Easy Migrate.

Create a back up using an external hard drive or a subscription program like Carbonite. This back up will be valuable in the future.

Partition your hard drive. Partitioning creates a second virtual hard drive by splitting the space into two or more separate containers. Use a commercial disk-partition program such as Norton's Partition Magic, Acronis' Partition Manager or a free program like GParted. Vista has its own partition tool: click "Start," then type "diskmgmt.msc" in the Run box and press "Enter." Follow the instructions very carefully. Divide the hard drive space into a partition or "volume" for your current OS and files, and a volume for your new OS. Set your oldest OS to boot first in the disk 0 volume. The disk 1 volume will contain the new OS.

Place the new OS Set Up disc in the CD drawer and reboot. If the Set Up disc doesn't run automatically, reboot and press F2 to enter BIOS. Tab to Boot or Boot Order and set your CD drive to boot first. Press "F10" to save your changes and reboot. When your computer reboots, it will find the OS Set Up disc in the CD player. The Set Up program will tell you there is a current Windows OS on one partition, but there is a second partition available. Choose this second location to install your new OS. Follow the on-screen instructions very carefully.

Reboot. Choose which OS to boot to now and press "Enter." If you don't make a selection, the computer will start the old OS by default.

Provide any needed driver support for the new OS. Your new OS may need its own drivers for devices on your computer such as a video or Ethernet card. Download drivers specific to your new OS from the computer or device manufacturers' websites.


  • check "Missing drivers" errors are common after setting up a dual boot system. A free tool like Everest Home Edition will help identify all the devices on your computer and point you to driver locations on the web.


  • close Do not attempt to partition your hard drive until you have made a back up of your current personal files. Make sure you have your original OS Set Up discs available in case re-installation is necessary to restore your machine.

Items you will need

About the Author

A writer and entrepreneur for over 40 years, J.E. Myers has a broad and eclectic range of expertise in personal computer maintenance and design, home improvement and design, and visual and performing arts. Myers is a self-taught computer expert and owned a computer sales and service company for five years. She currently serves as Director of Elections for McLean County, Illinois government.