Windows 8.1 won't update

If Windows 10 fails to install using the file downloaded from Windows Update, you can create your own installation media with this tool:

https://www.microsoft.com/en-gb/software-download/windows10

However, it's advisable to check HP's support site for additional information regarding the updgrade. Your Windows Update log identifies your computer as a Pavilion 15, but it doesn't state which model it is.

This is the support page for one of the model 15 series and you can change it to the correct one from there: http://support.hp.com/us-en/product/HP-Pavilion-15-p000-Notebook-PC-series/6936226/model/7279461/document/c04876361/

Also, the Pavilion 15 series is equipped with one of the latest 6th generation Skylake processors which are optimized for Windows 10: http://www8.hp.com/us/en/ad/windows-10/win7supporteddevices.html

If the installation proves to be successful, this site has a large number of tutorial on how to do things: http://www.windows10update.com/windows-10-tutorials/

I think you could have a go at installing Windows 10 now if you still want to. This same update is available in Windows 10 as KB3147461: https://support.microsoft.com/kb/3147461

However, you don't have the luxury of being able to disable automatic updates in Windows 10 and once that's installed, you have to accept everything Microsoft wants to install on your machine.

There are also the privacy issues to contend with although to a certain degree, you can disable a large number of them: https://fix10.isleaked.com/

Similarly, Microsoft has blocked other browsers from using Cortana now although some workarounds have appeared. But I suspect these will be shortlived: http://searchengineland.com/microsoft-says-no-to-other-browsers-248381

Windows 10 also uses your bandwidth to send other users updates: http://thenextweb.com/microsoft/2015/07/30/windows-10-steals-your-bandwidth-to-send-other-people-updates/

In your current situation though, I'm afraid to say that I don't know what else you can try to get the update installed. But this isn't the first time something like this has occurred and Microsoft has in the end come up with a fix. But it's anybody's guess how long that will be in this particular case.

I think I've tried all that before, but I tried it again and still no difference, they say it was repaired, but it still fails to configure the update and undoes the changes.

OK I think we're getting somewhere at last. According to the log file, KB3146723 extracts successfully and installs. However, during the reboot, it fails due to some missing system files which triggers error 0x80070002. The following Fixit addresses this issue.

https://support.microsoft.com/en-us/kb/910336

After the Fixit finishes, try and install the file once more.

If it fails again, do this next:

Open a Command Prompt (Admin) and then copy/paste the following commands and hit Enter after each one:

net stop wuauserv

net stop bits

rename c:\windows\SoftwareDistribution SoftwareDistribution.old

net start wuauserv

net start bits

Try to install KB3146723 again.

If it falls over in spite of the above, open a Command Prompt (Admin) and copy/paste:

DISM.exe/Online /Cleanup-image /Restorehealth

After DISM finishes and assuming it fixes any corruption (take a screenshot of that if there's any mention of that) and then try to install KB3146723 again.

OK, I download it, but it might take a while to figure out what's going on. I'll let you know a.s.a.p.