If you're looking to learn how to make really outstanding DesktopX widgets, you need go no further than RomanDA's ongoing tutorial series here at WinCustomize.com.  Just this morning, he posted part 5, focusing on WMI to extract all sorts of interesting and useful data directly from your Windows operating system.  This is very useful for people looking to make drive, CPU and RAM meter gadgets.  The tutorial walks you through all of that from start to finish, though you will have to have gone through the first four parts of the series to have a really good idea of what's going on.

If you're new to the series, you can hit up this article here that tracks all the parts as they're posted.