The Windows 8 Release Preview is ready for download in ISO format from Microsoft’s servers:
Product Key: TK8TP-9JN6P-7X7WW-RFFTV-B7QPF
Burn Windows 8 Release Preview ISO to a DVD
Follow this guide to learn how to burn an ISO to a DVD.
Create a bootable Windows 8 thumb drive
Use this method if you use a netbook (with no DVD drive) or just want to install Windows 8 from a thumb drive.
Install Windows 8 in a Virtual Machine
If you want to try Windows 8 from the comfort of your Windows 7/Vista/XP installation, consider installing Windows 8 in a virtual machine with VirtualBox.