Windows 7: Activation problem

I Purchased a Toshiba with Windows 7 Home Premium -didn't activate - didn't realise I had to. Installed Ultimate - Control panel says Windows 7 Ultimate, but now asked to activate as this copy of Windows is not genuine. Initial key and Ultimate key no good, as Ultimate for upgrade, not clean installation.
Instruction says run Windows 7 SetUp or enter Ultimate key- which obviously does not work.
I don't have original disks as system pre-loaded. Any suggestions to solve this activation problem.
Thanks in advance

Take look here.
Activate Windows 7 by Phone
Activate Windows 7 Online

Unlock all versions in your Ultimate DVD, reinstall Home Premium using the Product Key stickered to the machine.

To unlock all versions, extract the ISO from your DVD using ImgBurn, then run this: Ei.cfg Removal Utility Lets You Use Any Product Key With Your Windows 7 Disc

Now burn an All Versions DVD to reinstall Home Premium with your Product Key from COA.

Immediately activate at the Computer>Properties activation link.