Windows 10 May 2019 update is blocked on PCs with USB drives and SD cards
(Windows Phone Central)

All you need to do is remove external storage devices before installing the May update. You can get your hands on Windows 10`s big May update before everyone else, but you should remove your external storage devices before you proceed. Windows 10 May update has a weird bug where it was found to be reassigning drive letters for external storage devices. For instance, if you have a USB hard drive that shows up as the D: drive, the update could shuffle it to the E: drive. As a result, Microsoft is blocking the update from installing on PCs that have USB storage or SD cards attached to them: Inappropriate drive reassignment can occur on Windows 10-based 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 com...