I have not determined what a minimum system is, but if you have at least the following, you should be ok.
But then, its free software. Just try it and see if it works for you.
2 GHz processor, with 512 Meg memory
3D graphics accelerator with OpenGL support
Not much disc space. 4 Mbyte
You also need a 4 axis joystick to fly HeliSimRC.
Typically an RC "transmitter" like box with two 2-axis sticks is used to be as realistic as possible.
I refer to your control box as a transmitter, even though it may not technically be a genuine RC transmitter. Its just terminology.