Can windows vista home premium be installed over the top of vista ultimate?

[camdijk]

I have lost my vista ultimate cover with the keycode. I have been getting a screen come up telling me that unauthorised changes have been made to windows and I have to reactivate vista ultimate. I still have my previous version (vista home premium) but it won't accept that keycode.

[timebomb]

If you can use the computer try using this program to tell you the activation code of your Vista Ultimate then just reactivate it.

http://download.cnet.com/Keybits-Product-Key-Viewer/3000-2094_4-75547684.html