Microsoft's first attempt to roll out a "Windows as a Service" upgrade is in progress, but the jump from Windows 10 RTM to version 1511 (aka Fall Update and Threshold 2) has not been trouble-free. Here are some of the problems you may be experiencing, as well as a few solutions.
Realize that the v 1511 upgrade is not a cumulative update: Microsoft downloads about 3GB of files, and the installation can take 30 minutes or more.
The Microsoft Answers forum yielded an answer -- from Microsoft, no less -- when poster Waseemulla S asked:
When installing the Windows 10 November update, progress gets stuck and hangs at 44%. How do I resolve this issue?
'Softie Anannya Podder came up with the answer:
We've observed that some devices that have an SD bus with an SD card inserted while installing the Windows 10 November update will stop responding at 44%, and we are currently investigating the issue.
If your install is freezing at 44%, check if you have an SD card inserted and remove it, and the update should be able to progress beyond this spot. If you needed the SD card for additional disk space, see if you have a USB/Mini-USB port available that you can use instead for the upgrade. Otherwise, you may have to try freeing up some disk space off the hard drive.
Of course, freeing up 20GB (the estimated install space) on a small device could be something of a challenge.
There's a thread on Reddit that describes how many software products are removed when upgrading to v 1511. Among the programs mentioned: CPU-Z, speccy, 8gadgetpack, a Cisco VPN client, SATA drivers, SpyBot, RSAT, the F5 VPN, and HWMonitor. Apparently moving from Win10 RTM to v 1511 is similar to upgrading from Win7 or Win8.1 to v 1511, except there's no advanced scan to warn you what will be removed. Fortunately, there's a list of removed apps that appears in the notification center when you boot.
If you're having other problems with the upgrade, first take a look at the Windows Update FAQ. I was personally surprised to see this admonition:
If it's been less than 31 days since you upgraded to Windows 10, you won't get the November update right away; this will allow you to go back to your previous version of Windows if you choose. After the 31 days have passed, your PC will automatically download the November update.
That explains why the upgrade hasn't appeared on my main system.
Also, per the FAQ:
If the setting to defer upgrades is turned on, you may not get the update immediately. To make sure this setting is off, select the Start button, then select Settings > Update & security > Windows Update > Advanced options, and clear the checkbox for Defer upgrades.
Finally, an important note for anyone who rolled back from v 1511 to the RTM version:
If you uninstalled the November update from your PC, you won't be able to install it again from Windows Update. Instead, you'll need to go to the Microsoft software download website and select Upgrade now to upgrade your PC to Windows 10 Version 1511, which includes the November update.
If you're having problems with the update, go to the Microsoft Answers forum and post a question/complaint in the Windows Update topic. Leave us a trail here, too, or on AskWoody.com. We'll see if we can come up with some solutions.