Microsoft will block upgrades to the Windows 10 May 2019 Update if external media such as a USB device or SD card is attached to the computer. This is being done as USB devices can have their drive letters reassigned during the upgrade.
According to a new support bulletin by Microsoft, if you attempt to upgrade to the Windows 10 May 2019 Update from a computer running the April 2018 Update or the October 2018 Update, the upgrade will be blocked if external media is attached.
This is because USB drives or SD cards could have their drive letters reassigned in a way that causes a conflict with other drive reassignments or prevents necessary software to properly load after an upgrade.
"Inappropriate drive reassignment can occur on eligible computers that have an external USB device or SD memory card attached during the installation of the May 2019 update. For this reason, these computers are currently blocked from receiving the May 2019 Update. This generates the error message that is mentioned in the "Symptoms" section if the upgrade is tried again on an affected computer."
When this happens, Microsoft will display an error that states "This PC can't be upgraded to Windows 10" as shown below
Windows 10 May 2019 Update Blocked ErrorIn the
support bulletin, Microsoft provides this example of drive reassignment:
"An upgrade to the May 2019 Update is tried on a computer that has the October 2018 update installed and also has a thumb drive inserted into a USB port. Before the upgrade, the device would have been mounted in the system as drive G based on the existing drive configuration. However, after the upgrade, the device is reassigned a different drive letter. For example, the drive is reassigned as drive H.
Note The drive reassignment is not limited to removable drives. Internal hard drives can also be affected."
Removing external media, unnecessary DVD/CDs, and unplugging printers have long been a
recommended method to get past problems upgrading or installing Windows 10.
Similarly, Microsoft states that users will first need to remove any external media such as USB drives and SD cards and then reboot the computer. Once the computer is rebooted, they can then attempt the May 2019 Update again.
Microsoft has also stated that this issue will be fixed in a future Windows 10 servicing update. For Insiders, it will be resolved in build 18877 and later.
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