There currently is a bug in Windows 8 & 10 which sometimes prevents HVAC-Calc from displaying the Tree on the left hand side properly.
This problem only occurs if there is a touchscreen and even then only on some computers, not all.
The program runs fine on all Windows 8 & 10 computers if there is no touchscreen.
Hopefully Microsoft will soon fix this bug, however in the meantime, if you are one of the unlucky ones, there is a workaround.
The way to work around this bug is to temporarily disable the touch screen AND touchpen if present. This is not hard to do and the touchscreen can easily be re-enabled at any time.
Here are easy instructions to disable and enable the touchscreen.
Microsoft has recently made it easier to do since these screen shots were taken as they have improved the labelling so you can actually see what devices are there. Why they didn't do that in the beginning is hard to understand.
1. Hold down the Windows key and press the letter "X". This brings up a menu with Device Manger on it.
2. Click on "Device Manager".
3. Click on the little triangle to the left of "Human Interface Devices". (Or double-click on "Human Interface Devices")
4. There are several HID devices listed. One of them is for the touchscreen but we don't know which one, so we will use trial and error.
So, right click on the first instance of "HID-compliant device". If yours are labelled, then you can just disable the touchscreen and touchpen.
5. This brings up a little menu. In the menu click on "Disable" and say "Yes" to the pop-up. Now test your touchscreen to see if it responds
to your touch. If it does, then right click again and re-enable the first one and try the second one. Keep going until you find
the correct one for your touchscreen. It is usually in the first three. Don't forget to re-enable each of the wrong ones.
6. We are done! Your touchscreen is turned off. You can turn it back on anytime you want. You
can see which one is disabled by the little arrow on the icon.
7. Now you can click on the red "X" in the upper right of Control Panel to close it and use HVAC-Calc.