Here is the process to install Windows 8 from a USB drive, Dual-boot with XP, Vista and 7
Step one
If you're not sure what version of Windows 8 to download, we'd recommend the 64-bit build, especially if your system is relatively modern. You can read more about the difference between 32-bit and 64-bit operating systems here and the download page linked above provides system requirements for each architecture. The short of it: Windows 8 64-bit requires an extra 1GB of RAM and 4GB of storage -- negligible for most users. Also, before you ask, the Windows 7 USB/DVD tool will work fine with Windows 8.
Step Two
Create a bootable Windows 8 USB drive
Naturally, to create a bootable USB drive, you'll have to insert one and it needs to be 4GB or larger. Install the Windows 7 USB/DVD tool. Once the utility opens, you should be able to browse for and select the Windows 8 ISO you downloaded as well as the USB drive you inserted. It's worth noting that your USB drive will be wiped, so save anything important. The process takes about five minutes depending on the speed of your drive. You'll see a message that reads "backup completed" when it's done.
Step Three
Install the Windows 8 Release Preview (key: TK8TP-9JN6P-7X7WW-RFFTV-B7QPF)
Needless to say, back up anything important before proceeding. If you plan to upgrade or overwrite your installation of Windows XP, Vista or 7, open the root directory of your USB drive in Windows Explorer and launch Setup.exe to begin. You'll get to choose between the two. Windows 7 users should have a painless upgrade as programs, Windows settings as well as user accounts and files are imported. However, Windows 8 won't save programs from Vista and it won't save programs or Windows settings from XP.
If you want to dual boot Windows 8 with your existing operating system, you'll have to install a second storage device or create a new partition. The former is relatively self-explanatory, just attach the drive and choose it during the installation process. The latter, however, requires a little more effort. Vista and 7 users can create a new partition with Windows' Disk Management application (Start > search for Disk Management). Once the application loads, you should see your operating system's drive. Follow these steps:
- Right click the drive that you want to house Windows 8 and choose "Shrink Volume" (Windows 8 64-bit requires at least 20GB, so shrink your current partition accordingly)
- Right click the new "Unallocated" space and create a "New Simple Volume"
- Choose the next available drive letter and quick format the partition with NTFS (you can name the volume anything, but we'd suggest something like Windows 8 RP x64)
Windows XP users will have make partition adjustments with a third-party tool such as Partition Logic, but you'll do the same thing: shrink one volume to create another. It should be smooth sailing from here as Microsoft's installation process guides you through everything. Just boot off your Windows 8 USB drive, choose a custom installation and select your newly created partition. If you're having trouble launching the USB drive, you probably just have to put it ahead of your system drive in the BIOS (look for boot options).
If you want to get rid of Windows 8, load your primary OS and launch partition software (again, Disk Management for Vista or 7 users). Delete the Windows 8 volume and extend your remaining partition into the freshly unallocated space. Removing Windows 8 could screw up your bootloader and prevent your original OS from starting properly. Don't panic, this is a simple fix. Windows Vista and 7 users can use the automatic Startup Repair, while Windows XP users will have to get their hands a little dirtier.
Source: www.techspot.com
