Wow. I don't know what you have against the HWINFO forum. Martin (developer of HWINFO) is extremely active on this forum and responds quickly to almost every post. When someone finds a bug or problem, there is typically a fix the same day. It just doesn't get better than that. If you want an example of a terrible forum, I would suggest checking out the Asus ROG forum.
I have the same question -- I have the .gadget file but no clue what to do with it. Putting it in the same folder as HWiNFO64.EXE had no apparent effect. Good stuff. Good, good stuff.
Since support for gadgets has been removed in recent Windows versions, you will need to install some 3rd party gadget support. Many prefer the 8GadgetPack. Some others prefer an alternate solution like Rainmeter.