ModelSim shows "wrong number of args for "dataset info"" - Error

I am new to Modelsim and wanted to simulate the successfull compiled vhdl-file from the tutorial:

LIBRARY ieee ;

USE ieee.std_logic_1164.all ;

ENTITY switch IS

PORT (x1,x2 : IN STD_LOGIC;

f : OUT STD_LOGIC ) ;

END switch ;

ARCHITECTURE LogicFunction OF switch IS

BEGIN

f <= ( x1 AND NOT x2 ) OR (NOT x1 AND x2 ) ;

END LogicFunction ;

The files are stored in C:\DT and Quartus refused to open ModelSim (Programm not found).

But the programm is installed and so I run it seperately and opened C:\DT\simulation\modelsim\switch.vho

Then ModelSim says# wrong number of args for "dataset info".

What do I wrong?