Activating Win7 OEM

Hi I bought the dell laptop with win7 professional 32bit (oem) already installed, last week I deleted the OS and made a clean install of win7 professional 64bit (from a downloaded ISO). I extracted the licence key with the jelly bean key finder but the activation failed with the error: 0xC004E003. Later on I find out that the key is hidden behind the battery, but it was a very different key...