The automated activation system usually denies multiple installations. Workaround is the phone activation system. I have never been denied a re-activation using the phone system and have loaded multiple systems off one OEM license in the past XP/Vista/Win7 numerous times. Key statements: "only installed on one system" <- they just have to hear this plus any form of the following: "Hardware failure, needed to replace HDD" "upgraded to SSD" "Darn OS crashed again, needed to re-format" "I reformat regularly to optimize performance"