"Couldn't update to Windows 8.1 - 0xC1900101 - 0x40017"

I think you haven't undertood the problem, most of the people having this problem, me included, are having this issue on new hardware and free of any software and driver that could give problem (and by the way shouldn't be this way, a big update like this should work independently of the software I've installed). I met this problem on a desktop I assembled from scratch, with a regular copy of windows 8, and with all the newest pieces of hardware you can find on the market. I ran windows update to get the pc ready for the 8.1 update and bam, this problem came, again and again, and at the end I asked for remote assistance and they solved the problem, didn't understand how, but they did it. So they know there is this problem but they don't care, then they don't have to complain if many people use a cracked or illegal copy of windows if these is the official assistance and care

I think you haven't undertood the problem, most of the people having this problem, me included, are having this issue on new hardware and free of any software and driver that could give problem...snip       

I do understand. Most of the time when I see these problems, it is on new machines that people built. Did you check all the hardware against the MS 8.0 compatibility list? Did all the hardware and drivers have the holographic tag certifying that it has passed the MS certification? Did you check the partitioning of the new drives to see if they were NTFS compliant, or, were they preformatted at the factory on a Linux based mass formatting production rig? (I can't tell you how many times I've been bitten by that.)

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The issue is not WHAT third party software you installed. It is WHAT that software DID to the OS.

Third parry programs that modify the OS, like ones that replace the start menu, add AERO, remove the charms, removed Metro, or replace the built in security with old antivirus programs designed for other operating systems, then the resulting OS becomes a mishmash.

You are no longer running Microsoft Windows, instead, you are running Mishmash Windows.

I bought a 7" Toshiba tablet through the MS store. They sell the exact same hardware at the exact same price as the identical model from Toshiba. Microsoft calls it a Signature Edition, Which means it comes without all the shovelware that Toshiba put on the same identical tablet. I upgraded it to 8.1, the upgrade went without a hitch and was done about 3 hours after taking it out of the box.

I got the MS Signature Edition because I had purchased the exact same tablet from Toshiba two weeks earlier and spent nealy all my time with tech support trying to get it to upgrade. The first problem we found was that the shovelware antivirus had to be removed,  it prevented the Store from modifying the windows system. That got us farther into the upgrade. Then there was a helper app for the USB, a WiFi driver and a couple other things that were crashing the install, all a result of the shovelware that Toshiba installed. I didn't get the tablet from Toshiba working until a week after I had the Signature edition from MS upgraded. I did it by making a USB 8.0 install drive, doing a clean install of 8.0 from MS and then upgrading to 8.1. After all that, the upgrade went just like the Toshiba Signature Edition from the MS store.

Francesco, You are right when you say; "a big update like this should work independently of the software I've installed". That is true. However, If you have some rogue third party programs that modify the OS via registry hacks and such, or change the underlying drivers or even the disk structure, then you have a Frankenstein Zombie Alien OS,  (FZAos) and a update will not know what to do with it. The 8.1 update expects Windows 8.0, not OSX, PS3 or FZAos. Even then, only some updates will keep your existing programs, other times, you will need a transfer utility, then, you might have some programs that will need to be upgraded or are not supported.

Frankly, I am impressed that the upgrade successfully returns your system back to it's original 8.0 OS once it finds that your 8.0 copy has been zombiefied. It successfully presents you with the error message, "Can't be upgraded" and "Your OS has been restored to 8.0" but to expect it to know how your system got zombiefied is expecting the impossible. Frankly, I would not want the upgrade to be a 9 TB of download to handle every possible piece of **** the hardware vendors put on PC's . "Can't be upgraded" and "Your OS has been restored to 8.0" is pretty good compared to what most other OS's do.

Bye the way ,Francesco, I'm impressed that you managed to build a PC with all the latest stuff. I've built more than a thousand PC's for engineering firms, power plants, paper mills and othe businesses. For the most part I used tried and trusted components. If I changed to a new board, I often put it in several PC's and threw everything I could at it before I added it to my stable of components. Sometimes I spent weeks selecting something as simple as a disk controller. To build a new PC from all new versions of components takes some real skill, not to mention chutzpah.

Tell me, Bob, how is any ole' layperson to know the difference between that Toshiba and a Toshiba

Signature Edition out of the box - exact you say?  Didn't you also say it was not exact? Same but

different? Same price and model but DIFFERENT?  Not getting in your face - but come on.....

seriously?  I should know this??  HOW? 

My machine is a Dell and just spankin' new - all I did was put in the anti-virus and tried to update.

Would not take, I stopped the anti-virus for a couple hours - obviously that didn't work.  I contacted

Dell and MS - and they both remotely accessed my desktop.  MS escalated (HAHA) to a bigger

helper - and he said - he couldn't fix it, so said it must be the update has been corrupted and he

would send me a brand new disk to update and that would fix it.  It did not.

After reading about the problems here - what some almost 900 comments - I completely took off

the anti-virus (with no help from Dell or MS to tell me to) and it FINALLY went through - after more

hours than I care to tell you about.  

Now it is months later and most probably a newer update coming down the pike - I've since added

more things to the computer - so, now what - take it back down to nothing just to update?  

Yep, understand what you are trying to say about the mishmash - well then since we nearly all will

have some mishmash or another - why even bother to update? What is the point if they

can't keep their system mishmash proof?

I pretty much gave up on the upgrade some months ago after a dozen tries. Not worth the frustration. This is a one year old Dell Win8 with all the updated drivers. Oh well.

But did get to thinking. Of  the experts on this forum, would booting to safemode with networking be successful? All the added s/w would not load, and it would be simple vanilla Win 8

Bob, I think you made some good points but you missed the fact that Microsoft has stoned-walled most of us on this problem and to this date has not officially acknowledge that the problem exists.  If they at least gave some of the explanation you gave as to the root cause, many of use would be at least more understanding why 8.1 won't install as a simple update. And I'm not even touching on the poor MS support nor the multitude of clean, uncomplicated configurations that should have worked but didn't.  

Bottom line, a poor way to do business - sorry, there is no excise for it from a company that was as reputable as Microsoft.

David B.