Windows 8.1 Preview:
Windows 8.1 Preview
is a testing version not the final version and you might face problems while using the OS. So its better to install Windows 8.1 Preview in a separate partition on your computer system for testing purposes.
Why should not upgrade Windows 8 or other Windows versions to Windows 8.1 Preview?
You should not upgrade Windows 8 or other Windows versions to Windows 8.1 Preview for 2 reasons:
1. First reason is that if you upgrade your existing Windows version to Windows 8.1 Preview, you'll not be able to uninstall the Preview version in future. You'll need to reinstall previous Windows version using setup or recovery disc.
2. Second reason is that when Windows 8.1 final version will release and you decide to upgrade Windows 8.1 Preview to final version, you'll not be able to keep your 3rd party software and apps which you installed in the OS. You'll need to reinstall them.
So, what should i do?
If you want to use Windows 8.1 Preview as your primary OS, sure go ahead. I'm also using it as my main OS but install it on a different partition and don't remove or upgrade your existing OS. Why? Because if something goes wrong in Windows 8.1 Preview or if you don't like it in future, you can go back to your previous OS.
Or its better to install Windows 8.1 Preview in a separate partition on your computer system for testing purposes. You can also install it in a virtualization software such as Virtual Box or VMware.