When I run the 5.1.1 installer without administrator privileges and deny admin rights (or wait long enough for the dialog to time out) it comes up with a message box telling me to restart the installer with root privileges or start an admin command prompt and start the installer again using "--startserver ...". When I try the second suggestion installation seems to continue but fails when it tries to install vcredist telling me:
Error during installation process (qt.tools.vcredist):
Execution failed: Could not start: "D:\Qt\Qt5.1.1\vcredist\vcredist_sp1_x86.exe /norestart /q"(Process failed to start: The requested operation requires elevation.)