How to dual boot Windows 8.1 with Windows 10 Preview January 12th, 2015
Don’t upgrade Windows 8.1 to the Windows 10 preview on a PC you depend on for everyday use. A “Dual Boot” setup a far better choice.Just reboot to switch between Windows 8 or 8.1 and Windows 10. It’s the best way to compare the differences.
Want to try out software that’s still in development and like sharing your opinion about it.
Don’t mind lots of updates or a UI design that might change significantly over time.
Really know your way around a PC and feel comfortable troubleshooting problems, backing up data, formatting a hard drive, installing an operating system from scratch, or restoring your old one if necessary.
Know what an ISO file is and how to use it.
Aren't installing it on your everyday computer.
Things to keep in mind:
Unexpected PC crashes could damage or even delete your files, so you should back up everything. Some printers and other hardware might not work, and some software might not install or work correctly, including antivirus or security programs. You might also have trouble connecting to home or corporate networks.”
For Windows 7, 8 and 8.1 – You Keep: Windows settings, personal files, and most apps
There is a good chance that some of your applications that run fine in Windows 8 / 8.1 are not even Windows 10 compatible. You would also be in the position of forking out more money just to purchase a Windows 10 compatible version (if anything is available at this time) of software you already own, paid for and works just fine in Windows 8.
2) There is no guaranty that you will be able to upgrade from a Preview Version of Windows 10 to the final “Retail” version when it becomes available next year. If you can’t upgrade that means the preview version is a dead end and you will need to perform a fresh (“Custom” / Clean) install of Windows 10.