I have written a .hdl file for the not gate. But when in the hardware simulator, if I load the not gate I just created it won't load at all.
First, make sure that you are loading the right file with the right load command. If you want to load your HDL file and poke at it to see what it does, use File>Load Chip to load your HDL file. If you want to test your HDL file load the corresponding TST file using File>Load Script, and the test script will load your HDL file. Note that the TST script and your HDL file must be in the same directory.
If this is not the problem that you are having, and there is an error in your HDL file, the simulator should be displaying an error message in the status line at the bottom of its screen. On small computer screens this message can be hard to see and you may need to move the window up to see the message.
If you can't figure out what's happening, you can send your Not.hdl to me using More>Reply to Author and I'll be happy to give you suggestions to get it working.