I need to upgrade Windows 2003 server SP2 standard to Windows server R2. I understand that I need the R2 disk 2 CD but when I use a disk 2 from another set, I get a notice that the product id is either invalid or if I proceed, Windows will have to be re-activated. I heard that Microsoft had an .iso that could be downloaded to upgrade without re-activating. Is that true & if so, how do I acquire it? I don't mind purchasing the upgrade if it is available also.