OK, it is too late to upgrade your Vista doing an in-place upgrade which reinstalls everything in the new Windows 7 since your VIsta is gone, right?
So now you are trying just to activate the Windows 7 you've got because otherwise it's okay?
If so, and you have tried inserting your Product Key when first asked by the installer, then made a second attempt by using the Activaton link on Computer>Properties page, and neither of those worked on this installation?
Then, yes, the next step to get activated is to do a Repair install, which with Windows 7 is a simple upgrade over the existing OS run from the desktop, by running the Windows 7 installer and choosing Upgrade.
WHile it is running, browse the comments in the tutorial
linked above so you can see how others resolved this, following these same steps.