IrfanView can do any sort of rectangular cropping you want. If it didn't work for you then you are using it wrong. Thus no black areas, as you've mentioned.

Suggestion: once you "rubberband" the area you want (that is where you left-click down and stretch out the corners of the rectangle) you just press Ctrl+Y to crop off all the outside areas.

2nd Suggestion: Once you have those crop lines down, and have not pressed the Ctrl+Y yet!, you can adjust any of the 4 edges by just selecting the edge and adjusting. This is useful since sometimes when you first start the crop lines you don't get it quite right.

3rd Suggestion: Once you have those crop lines down, and still have not pressed the Ctrl+Y yet!, you can right-click inside the marked area and drag around the set box without changing the area of the box.

4th Suggestion: After you have the pressed the Ctrl+Y and actually cropped the area you thought you wanted, but if you now found out you don't like it, you can either:
press Ctrl+Z to undo the crop, or
press Shift+R to reload the original picture again.