Windows 8 will be broadly available on Oct 26th. If you are planning upgrade your Windows 7, Windows Vista, Windows XP computer or laptop to Windows 8 Pro, You can use Windows 8 Pro upgrade at windows.com. It just costs $40. This is for upgrading your existing Windows computer.
If you want to keep your current Windows computer as it is & you don’t want to upgrade existing OS, you need to buy Windows 8 Pro System Builder DVD. You can use this on a new partition for dual booting or virtual machine etc. If you have old Windows computer like Windows 2000 etc, You need to use Windows 8 Professional System Builder software to install Windows 8.
Where to buy Windows 8 Pro Full DVD with Windows 8 System Builder?
Amazon has Windows 8 Professional System Builder DVD. You need to use this If you don’t want to upgrade existing Windows 7, Windows Vista, Windows XP installs. You will lose existing personal files. You need to make a backup before installing this full Windows 8 Pro DVD. As You don’t need to pay taxes in most states on Amazon, This may be the cheapest deal to buy Windows 8 Pro full DVD
Make sure to buy 32bit or 64bit Windows 8 Pro Full OS depending on your computer processor.
Also, read comparing Windows 8 or Windows RT tablets