I think I know, but how do you install full oem over an existing drive? From what I'm reading upgrading to Windows 7 Home Premium might not be ideal for me. So if I order the OEM version and want to install it on a drive or two drives in raid 0 that I have Vista on, don't I just install the disk and it then give me the otion to over right or delete the existing operating system and install Windows 7? It's been a few years since I've done this.