Hi, do you have installed the last Excel Patch KB905756 before ?
Yes, than you have to delete the following reg keys, then sp2 update should
run
HKEY_CLASSES_ROOT\Installer\Patches\188A70814A751974F81247587F581A1E
HKEY_CLASSES_ROOT\Installer\Products\9040110900063D11C8EF10054038389C\Patches