Get the Retail version...I probably will be changing if i upgrade as it will be a whole new build.
I think retail is the way to go thanks again!
Single PC new build? Go for OEM with W8 around the corner.
Otherwise go retail, then transfer the license to another PC when you upgrade to W8.
That said, I've got W7 retail, just upgraded mboard/CPU and while it rebooted in W7 smoothly and sorted out the drivers with no issues it tried and failed to revalidate last night (now got the black screen and "this does not have a genuine license" message) - hoping it was just an issue with the MS licensing servers as revalidation was complaining that the process was failing to complete and that it will work when I try again today!