I recently had a similar issue on my machine (Win 7) and had to do a full uninstall/reinstall to correct everything. Do you have an active VAR subscription? If so, they can send you some documents on how to resolve this---possibly without having to do a full uninstall/reinstall. I was surprised how much of the uninstall/reinstall process had to do with Windows services and the .NET components, specifically.
Hmm...I don't think I have a VAR. It's through my university. I emailed them today.
..yeah... not a easy one.... there are repair tools microsoft provides..
This is the general do all fix it...
..and,.. this site is more specific..
You may also see if the .NET stuff is turned on within Windows if Paul's links above don't help.
Here's an article that helps you do that, and in this case you'll most likely want to turn off the .NET 3.5 features, then reboot, then turn them back on and reboot again:
Thanks all. I will try the tips.
So, when I check Control Panel, Windows features has turned on (.Net 3.51) and in regedit for .Net, in HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Updates., .NET 4.5 strangely is there, which didn't appear in the control panel.
BUT i did notice that the particular file listed in the error message (KB2901907) is not present in the registry, which is causing the install failure.
I was able to correct the problem. I apparently had to do even more and more....and more....Windows updates until it decided to work.