Unable to create process using '"D:\python.exe" "D:\Scripts\pip.exe" install PyQt5': The system cannot find the file specified.

This error message suggests that the system is unable to locate the Python executable file located at "D:\python.exe". This could be due to a variety of reasons, such as incorrect installation or configuration of Python, a corrupted or missing Python file, or an issue with the system's PATH environment variable.

To resolve this issue, you can try the following steps:

1. Check that Python is installed correctly on your system and that the executable file at "D:\python.exe" exists.

2. Check that the system's PATH environment variable includes the directory where the Python executable file is located. You can do this by typing "echo %PATH%" in the command prompt and looking for the directory containing the Python executable file.

3. If the PATH variable is missing the directory containing the Python executable file, you can add it manually by editing the system's environment variables.

4. If the issue persists, you can try reinstalling Python and ensuring that it is installed correctly with the necessary components.

5. You can also try running the command prompt as an administrator to see if this resolves the issue.

If none of these steps work, you may need to seek further assistance or consult with a professional to diagnose and resolve the issue.