Some users are receiving error 0xC1900101 – 0x20003 during upgrade from Windows 7 SP1/8.1 to Windows 10. Here are a an explanation, what's the root cause and few tips/workarounds to overcome this error.
This error will bee seen on some systems with small eMMC or SSD capacity, if the the Windows drive is nearly full. The upgrade to Windows 10 seems to work at first. But somewhere during progress at 70 – 90 % the error occurs and a rollback reverts to the old Windows installation. Some users are reporting the following error explanation.
Error code 0xC1900101 – 0x20003
The installation failed in the SAFE OS phase with an error during the INSTALL_UPDATES operation
I've seen this error code also has been reported in forums as a Windows 8.1 upgrade attempt. The common tips to uninstall third party antivirus software, remove peripherals or do a factory reset are not really helpful.
Not enough free disk space
The error message shown above give us a clue, what went wrong. Windows setup was able to copy all install files to the install drive, move the old install to Windows.old and begin with further steps. Then the INSTALL_UPDATES operation failed due to missing free space on the drive.
Searching the web brought me to this Microsoft Answers forum thread. Microsoft employee Giridhar J wrotes:
You will experience these symptoms if you have just enough free disk space to pass the compatibility check for installing Windows 10, but not enough disk space for the additional updates that are installed during setup.
If you receive these errors on a device that has little free disk space, try freeing up additional space and try again. Depending on the device, you may need 10-13 GB of free space to install Windows 10. We're currently working on modifying the compatibility check so that it doesn't underestimate the amount of space required.
Also, disconnect all the external devices (printers, scanner, USB (universal serial bus) drives, etc…) Except mouse and the keyboard and then try to upgrade.
So the root cause is probably clear. But some users are reporting enough free disk capacity on the Windows install drive. I'm not depth enough into the detail of INSTALL_UPDATES phase – but keep in mind, that maybe a System Reserved partition is involved. And if there isn't enough free space, this could also be a show stopper. Another scenario may be a faulty driver (I/O disk driver, chipset driver, filter driver from third party antivirus software) that causes the error. In some cases a log file analysis (see) can deliver the clue what caused the error.
Workarounds are probably possible
Microsoft's employee suggests to free up 10 – 13 GByte space on the install disk and try again. Maybe the upgrade will be successful.
Another idea is, to block downloading and installing recommended updates. The setup dialog shown above (sorry, I have only a German screenshot) contains an option box to block downloading updates. If the Windows 10 upgrade went through, you are able to clean the system (deleting Windows.old). In a second step, Windows 10 will install the necessary updates automatically.
Some users are claiming enough free disk space on their Windows installation drive. But take care, also System Reserved partition could be updated – and missing free space will result in a rollback. Maybe some outdates drivers are the cause for this error (although the discussion here shows that this results in different error codes).
The most simple workaround will be: Download the Media Creation Tool, download the Windows 10 install image, and create a DVD or USB stick as an install media. Then save the old Windows installation via system backup. Afterward boot the machine with the install media and do a clean Windows 10 install (see). This shall result in a fresh and clean Windows 10 system.
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