This article applies only to Release Preview for Windows 10, version 1903 (currently available to Windows Insider Program customers only).
If you are part of the Window Insider Program, and you are trying to upgrade to the May 2019 Update for Windows 10 (Windows 10, version 1903), you may experience an upgrade block and receive the following message:
This PC can't be upgraded to Windows 10.
An external USB device or SD memory card that is attached to the computer could cause inappropriate drive reassignment on Windows 10-based computers 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.
Example: An upgrade to the May 2019 Update is tried on a computer that 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.
To work around this issue, remove all external media, such as USB devices and SD cards, from the computer. Then, restart the May 2019 Update installation.
This issue is resolved in Windows 10 Insider Preview Build 18877 and later builds, and will be resolved in a future servicing update for Windows 10.