It has been repeatedly stated to run a Beta OS, such as Windows 10 currently in the following ways:
It requires a physically separate drive be available but, this is, also, a method...
Running Windows 8.1
Unplug, disconnect the drive holding Windows 8.1
Install Windows 10 to the other drive.
Once done reconnect all drives.
You shut down & F12 to pick the drive you will boot, either 8.1 or 10.
This is not the same as dual-boot. They are distinct. They are each booting themselves separately; not sharing a boot ini.
Easy, safe and creates a very 'normal' set-up. Much better than a VM & even better than dual-boot. You can 'see' all drives from both OSs this way and all USBs or peripheral gear from both.