Windows Update error 8024402C

Doesn't work, still error code 8024402C.

Well, it seems we overlooked something in that document, or can't remember if we tried that already.
It's about the line in the Windows Updates screen where it says You receive updates: Managed by your system administrator
and under that you can click on Check online for updates from Microsoft Update. We did that and it started searching for updates and it found an update to download and install So that seems to work already.
However it was only one single update it found (probably one of the 3 we had to uninstall). However it is approximately half an hour ago since we started the download/installation of the update and it still busy at "downloading and installing updates", but I think that comes to the fact that the update might be big and also the fact that for some apparent reason, my friend's computer has become very slow at installing/uninstalling programs, since 2 years ago aswell. (pretty much during the same time he had the updates issue) But I think that is another story, we'll wait it out for now and I'll come back if anything interesting happens.

The installation seem to have worked. Update history said an update called Windows Update-agent 7.6.7600.320 was installed on 10/8/2015 (today)
However we still get the error code when trying to update on the "normal" way (pressing check for updates in stead of clicking on the blue Check online for updates from Microsoft Update beneath it)

Edit: oh you said it's SP1, ok. but the error code thing still isn't fixed. We're trying to do another update again, still searching now.

Ok, we checked for updates again through the blue text thingy.
Just take a look at it...:



It's in Dutch, but I guess I won't have to explain it...

So it seems to work when searching for updates with the blue text Check online for updates from Microsoft Update. (not system administrator which is blue in this screenshot, both options have changed position)
Any reason why? And how we could possibly get this to "default"?

Edit: And how should we install the updates? All at once or in groups?

Well we were sortof inpatient and we already started before you posted that
Guess it won't be that much of a deal, will it? Perhaps the IE updates.
What should we do if we would run into trouble after the installation process is finished? Uninstalling all the updates and starting over in the right order will be problematic.