Why can't I install Service Pack 1 on Office 2010 for my Windows 7 computer?

Brand new copy of Office 2010 on Win7 Home Premium, new install. Windows update repeatedly pulls up and alerts me of 'important' update for Office 2010 (SP1).

It has downloaded and failed to install over 20 times, even after I went back to an earlier Restore Point, and even after re-installing Office. Any suggestions?

Is it even important to do these 'important' updates? Office seems to be working fine but I hear much about security 'holes' that need to be patched, new features, etc. This update also says in rolls in all previous updates. Should I worry or quit trying.