I have 2 internal disks. On disk 1 (HDD) I have Vista. On disk 2 (SSD) I want to install Windows7. For the W7 installation I would disconnect disk 1 because I do not want a double boot but I use the BIOS boot sequence to switch between the 2 disks. I am wondering whether that is possible with the W7 upgrade edition (the $50 early bird offering). My Vista is an OEM that came with the PC and I only have the Installation/recovery DVDs that I burnt from the recovery partition. What I am wondering is how the W7 upgrade installation would know that I am eligible for the upgrade.