Right click on the update, select hide update then, for now at least it's gone until MS decide to force it on the OS I guess.
I have the same update (KB949810) on my W7 updates at this moment... except that I don't use Office 2007 - it's Office 2003...
Installed it three days ago - now I opened Excel 2003 and - guess what: This software is not genuine! (two nag-screens popped up)
Hmm... Skydrive (or at least the site with this OGAnotifer) seems to be down - "please try again later"..... And it's for quite a while now...
You can always uninstall a *.msi file, even if it doesn't show up in the add/remove programs. Paste the following command on the command line to uninstall the latest OGA: MsiExec.exe /x{B2544A03-10D0-4E5E-BA69-0362FFC20D18}