For those that would like to experiment with W8-DP on a computer with W7 or Vista and avast!
My current setup is W7 SP1 and W8-DP both running on a x64 desktop.
Install and Dual-Boot Windows 8 with Windows 7/Vista
http://techwalls.com/news/install-dual-boot-microsoft-windows-8/
Comments:
- You can only have one OS open at a time.
- To switch between OS it is best to first download and run
Tweak And Customize Windows 8 With Metro UI TweakerThis will place "restart.exe" on the Metro desktop. You need to do a Restart to switch OS.
http://www.addictivetips.com/windows-tips/tweak-and-customize-windows-8-with-metro-ui-tweaker/
- It is best to make W7/Vista the default on the boot screen.
- Avast will continue to work but only while you are in W7/Vista. Avast! will not update or run scheduled scans while you are in W8-DP. You will need to use another AV program while in W8. MSE works fine for this purpose though of course it is not as good as avast! I have not found any conflicts between avast! and MSE probably because only one runs at a time.
- If you keep your documents, pics, videos etc in a separate partition you will be access them in both W7/Vista and W8. Updates to documents like speadsheets while in W8-DP will be available when you switch back to W7/Vista since the documents are located in a non-OS partition.
- Of course you will need to reinstall any programs that you are using in W7/Vista that you would like to use in W8-DP. Firefox, Thundird and Open Office along with Malwarebytes, SAS among numerous other programs, though not all, will install and run in W8-DP without any problem.
W8-DP is very stable has some really cool new features, uses a lot less memory than W7 SP1 and is faster W7 SP1. 
Enjoy