i've now windows 7 ultimate edition on my system, i'm planning to upgrade to windows 8 Release preview to test the difference between both systems..
but the problem is that i'm worried about my programs, games and saved games that i've installed in windows 7, i'm feeling that it would be all vanished after upgrading to windows 8 , so i need to know for sure, if i'll be able to save my programs and games and their saves after installing windows 8 ? or just i need to re-install it from the beginning ?
I would avoid upgrading to a beta version of an OS regardless. Upgrading to a beta release of some application is one thing. Upgrading to a beta release of a whole operating system is another story.
Best bet is to back up your data and do a fresh install. The included Windows 7 'Backup and Restore' feature (found in Control Panel) is great for this, because you can tell it to create a whole system image as a .vhd file - which you can also natively boot from after the move to Windows 8 in case you need to do something in Windows 7 that won't work in a VM.
Edit: Case in point - I have one application that needs to be updated by the vendor to work under Windows 8 which loads it's own drivers (the drivers are there to enable a certain feature in the programs and are what don't work under 8, thus the program itself loads, but is crippled somewhat). I have a .vhd of my old Windows 7 install that I placed on to an SSD and added an entry in Windows 8's boot manager. When I select the Windows 7 entry, the system boots from the .vhd file as though I have natively installed the OS on that SSD. When I modify anything in Windows 7, the changes are saved back to the .vhd file on the SSD and are persistent across reboots of the physical box.
You need another hard disk to install the preview on. I have been using it on my folding@home machine for some time. I don't recommend it over Windows 7. There really is nothing new for desktop users thats actually better.
Interesting about FOLDING...
A lot of my machines run SETI.... did you notice any increase in units of Folding using 8 ?