Manual install of missing update

Checking Windows Update shows that there are no uninstalled critical or important updates for my computer (with the exception of the upgrades to IE10 and IE11, which I have hidden). I ran Belarc Advisor, however, and it shows that a critical update, Q2604121 ("MS12-035: Description of the security update for the .NET Framework 4 on Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2: May 8, 2012") is missing. I do not understand why this update is not offered/available to me through Windows Update. I did, however, download what I believe is the appropriate file, NDP40-KB2604121-x64.exe and saved it to my desktop. Before I install it I would appreciate any information about potential problems I might encounter or suggestions about preventative measures I should take beyond creating a System Restore point first.

Thank you for your help!

I suspect that this ay be a false positive caused by some minor corruption - but it could indicate more problems.
My system doesn't have this update installed, and doesn't show the update as missing in Belarc - this usually means that the update has been superseded and is no longer relevant.

Just in case -
Please follow the Windows Update Posting Instructions and post the requested data

Thank you for replying! I can't take the time to follow the above procedure right now, but when I have the data available I will post as directed. Just curious, though, is there a potential problem doing the manual install mentioned in my original post?

I suspect that it will simply fail - it shouldn't of itself hurt, though (unless there are already problems present, in which case it may make them more complex to solve)

I am going to close this question for now, as dealing with the issue has had to go to the bottom of my to-do list. I hope marking this "solved" isn't an improper action.

Thank you for your responses!

It's your thread - and your computer. :)