The latest news out of MS shows that Windows 8 Pro will be able to be Upgraded as Follows:
Microsoft writes that the types of files that can be transferred over vary based on your OS version:
You can transfer these… When upgrading from… Windows 7 Windows Vista Windows XP Applications x Windows settings x x User accounts and files x x x
"The Windows 8 Upgrade Assistant will check to make sure your PC is ready for Windows 8. It will provide a detailed compatibility report that lets you know of anything you may have to address before or after the upgrade and outlines actions to take.
It will also inform you of any application or device compatibility issues. It will ask you what you want to keep from your current Windows installation. (See chart above) You will be able to upgrade from any consumer edition of Windows 7 to Windows 8 Pro and bring everything along which includes your Windows settings, personal files, and apps. If you are upgrading from Windows Vista, you will be able to bring along your Windows settings and personal files, and if you are upgrading from Windows XP you will only be able to bring along your personal files. Of course, if you want to start fresh, you can choose to bring nothing along. Or if you prefer to format your hard drive as part of your upgrade experience, you can do so as long as you boot from media and then format your hard drive from within the setup experience for installing Windows 8, not prior to it."
Always burn the ISO file to DVD. The DVD includes the Repair Console when needed. In my case I will be formatting the partition while I install Win 8 Pro. I believe this gives me a much cleaner OS. I do know that many of you reading this will not do this and will simply upgrade thus saving your files, apps, etc. Unfortunately those of you that have suspect installs to start with will have suspect installs of Win 8.
We Moderators and senior members of this Forum and any new members that wish to help answer questions will get very busy after Win 8 is released because there will be hundreds of people that do not follow these instructions and will install inappropriately.
The steps involved are pretty straight forward.
Buy Win 8. You will be sent an email with the key and with links to re-download the ISO file if you forget to burn it to DVD and a link to buy a DVD if you choose not to initially.
You will then be given the option to install now, Install from the desktop icon or Save Nothing.
Choose Save Nothing
You will then be given the option to save the ISO file to your PC and to burn the ISO file to either DVD or Flash Drive, Save it to somewhere on your PC and choose Burn to DVD.
When done, boot to the DVD and choose Custom Install
On the next screen click the Advanced Disk Options and highlight your partition and then choose format.
Once the format finishes start the installation.
Once installed have fun customizing and installing apps.