As we know Windows 8.1 Preview update is for testing purpose and is not meat to be installed on our main OS. It is recommended to either install it on other partition as a dual boot or install the Windows 8.1 Preview in a virtual machine software like VMware Player and VirtualBox which are free and easy to use.
Before proceeding any further, you must have VMware Player, ISO file of Windows 8.1 Preview and the product code (NTTX3-RV7VB-T7X7F-WQYYY-9Y92F).
Then follow these steps:
- Open VMware Player and select "Create a New Virtual Machine".
- Select "Installer disc image file (iso)" and click Browse then navigate to the location where the Windows 8.1 Preview ISO file is located, select it and click Open.
- Click Next, select "Microsoft Windows" under Guest operating system and "Windows 8" under Version for the 32-bit variant or "Windows 8 x64" for the 64-bit edition.
- Type a new name under Virtual machine name -- preferably "Windows 8.1 Preview".
- Select the location of the virtual machine and make sure you have at least 16 GB for the 32-bit Windows 8.1 Preview and 20 GB for the 64-bit Windows 8.1 Preview, of free storage in the selected location -- 30 GB is recommended to avoid running out of space.
- Select "Store virtual disk as a single file" to keep the virtual HDD in a single file and optimize performance, then click Next.
- At the next screen click on Customize Hardware..., go to Memory and select a minimum of 1 GB for the 32-bit Windows 8.1 Preview and 2 GB for the 64-bit Windows 8.1 Preview. But, you should double that amount for improved results.
- At the Processors dialog box, under Number of processor cores, select the option available to your CPU. For a single core CPU it is one, for a dual-core CPU it is two, for a quad-core CPU it is four and so on -- this is to ensure the virtual machine is running at optimum parameters.
- Click "Close" then "Finish" to complete the virtual machine creation process and press "Play virtual machine" to install the Windows 8.1 Preview.
I prefer VMware Player over VirtualBox but if you are a VirtualBox user then follow this guide.
Source: Betanews.