Windows anytime upgrade and Windows 7 Service Pack 1?

I purchased a windows anytime upgrade product activation key from windows 7 starter to home premium, however when i click upgrade on the download utility tool it just tells me that the key is not the right upgrade key for this version of windows. Phoned microsoft and they said that it could be to do with the windows 7 service pack 1 which is preventing the upgrade from happening and that it needs to be uninstalled, however i have discovered that it cant be if it came already preinstalled on the computer, Now im annoyed as that means I cant upgrade to home premium from starter, is there anyway around this please help!!!