None of these problems can be reproduced, and don't happen under normal working conditions.
Please note that 'api-ms-win-core-libraryloader-l1-2-0.dll' is a Windows component, not part of PixInsight. This file should be present in a normal operating system configuration on Windows. If your system lacks this or other files pertaining to the operating system, please contact Microsoft's support to solve this issue.
As for the rest of issues being reported here, such as the 'black GUI' that you are describing, this cannot be reproduced either, neither on Windows nor on any supported platform. However, the most probable cause in this case is a defective and/or outdated graphics driver. Again, please note that we cannot be liable for problems caused by wrong implementations of required standards in hardware drivers, such as a defective OpenGL implementation in your graphics driver. Unfortunately, these problems are quite frequent on Windows, especially on Windows 7, where some drivers are not being updated correctly to support new software with strict standards compliance requirements.