Note :- Do not install it on the same partition where your current OS resides. Use the ISO file instead of Windows 8 installer to avoid losing your current OS. Do it only if you understand what you are doing.
Windows 8 has already created much hype in the market and if you are also willing to try your hands on this OS before it is launched, here is your chance. Windows 8 Release Preview is available for download on official Microsoft website.
Before moving ahead check out this video to know what exactly it looks like. This article is only meant for those who does have some prior experience in installing operating systems and understands the consequences of failure. Keep your recovery disk ready before moving ahead.
Video credits : LifeHacker.com
There are two options available for downloading and installing Windows 8 on your machine. First is you can use the Windows 8 Release Preview setup provided by Microsoft which will guide you through the installation . Second option is downloading the iso file from the link given at the end and burning it on DVD to install it. I will advice you to download the iso file and burn it on a DVD.
After burning the iso to DVD you can install it similarly as you would install any other OS. Installing this on the same partition as your old OS will overwrite your previous OS and you will not be able to recover it. So make sure you are installing it on a separate partition. If possible I will post a step by step procedure on how to dual-boot Windows 7 and Windows 8 release preview. Till then you can try it on your own (obviously at your own risk).