For anyone else who has this problem here is how I solved it.
First off the whole process was a nightmare. Just letting you know.
I tried a lot of things and it eventually worked. I'm going to list everything I did but my suspicion is the most important thing I did was frequent disk cleanups.
Instead of trying to straight update to windows 10 I updated 8.1 as much as it would let me. I had my HDD partitioned and the C drive only had 150 GB so after a billion windows update failures I figured maybe it would at least speed things up if I reclaimed the other partition. It was during this process that I did a disk cleanup (Had to click on advanced so it would search for more things to delete (e.g. windows update files)). After this windows update FINALLY worked.
If you get it downloaded and it freezes on preparing to install I'd try disk cleanup again and start over.
That was a 657MB download. The next windows update was a 15MB download. This took half a day. By the time it worked I had:
- turned off automatic updates
- disabled windows defender
- disabled all non-microsoft services and apps from running at startup
- ran troubleshoot > windows update (drag down from top right, type "troubleshoot", click it, click windows update) about 5 times
- restarted 4 billion times
- ran disk cleanup (again, i think this is the only thing that did anything). Please note that when it gets around to deleting windows update files that it will freeze. I found that killing the Windows Modules installer worker (windows update) breaks whatever deadlock the computer is in. e.g. the instant you delete it disk cleanup goes from a halt back to normal speed.
- defragged my hdd (this was after I restored the other partition)
I continued updating until it said I had no more updates to do (even optional). For me this was just another 85 MB update and it worked flawlessly. I never saw that update to windows 10 thing in the taskbar. I just googled "install windows 10" and clicked through the links once it was fully updated and to my surprise it worked (this was a 2 day ordeal).
One final thing to point out is that windows update is garbage. It will sit at "preparing to install" forever. It will download 700MB but leave it's download progress at 0%. It might not let you close it. It might not open when you open it. When I was upgrading from 8 to 8.1 it froze at 62% (permanently froze) and after some googling I found it will start again if you disconnect your internet and then reconnect it.
how long has it remained at 0%? – Moab – 2015-09-26T19:22:38.807
Do the dots spin? As long as they do you should assume all is still working. – LPChip – 2015-09-26T20:50:51.603
Yeah they spin. But here it is several hours later and still at 0. – user1526247 – 2015-09-27T04:28:21.683