ENVy Computer Compare ($10; free, feature-limited demo) is a powerful tool for reporting on the guts... and heart and mind and kidneys, metaphorically speaking... of your computer, and (once you buy the full version) comparing them to those of other computers.
When run, Envy Computer Compare does a thorough scouring of your system. Every part of your computer that can tell something about itself is queried, and the level of detail is extremely deep. There's almost no handholding when it comes to displaying the information; you either know what it means and why it's relevant, or you Google it, or you ask questions on an appropriate forum and hope you don't get laughed at. Usually, if you're using this kind of tool, you have a specific interest--registry settings or driver values, for instance--in mind.
The demo version of Envy will scan a local computer, but cannot import the results from another system. Envy Computer Compare earns its name when you buy the full version, which does compare-and-contrast reporting. (You must run Envy on one system and export an XML file, then import it on another.) While most comparison utilities use a side-by-side display, Envy shows all differences or similarities in a single column, using color coding to show which values are on one computer or another. This is an extremely effective way to display this type of information, as it is much easier to read down than across. The simple color coding rapidly becomes intuitive, and if you're looking for particular values, they can be found rapidly.
Envy Computer Compare is very useful for ferreting out information about your own system, which can be vital in a debugging situation or when you're trying to solve a problem on a forum and someone asks you your BIOS version (or any of a million other things). The comparison function is most useful when you expect two things to be the same. If software is working on one system but not on others, and it should, the use of Envy to track down likely points of conflict is obvious. Likewise, it's a good tool in environments where a "gold standard" is used for a clean system or default setup, and it can quickly highlight changes to a system. There's no network or remote function, so it will need to be run on each system that is to be checked; however, it does not require an install and can easily be run from a USB stick, making it a great part of any tech or support person's toolkit.
The one meaningful downside to Envy Computer Compare is that it can be quirky. When I reviewed an earlier version, called simply "ENVy," I encountered some odd behavior, and the developer quickly responded with bug fixes. When I reviewed this version... same story. Even so, I keep finding oddities; for example, the "Environment Variables" data imported incorrectly on my first try; when I closed Envy and tried the compare again, it worked. But then an unrelated progress window didn't close when it should, though I could still use the program.
Despite the limitations of the demo version (no comparison, will not report on file system or registry), it's still useful for a user who just wants to know information about his machine. If you regularly compare machines, either for support purposes, to audit security, or to better understand what's going on inside your computer, the $10 price is well worth it. Given the odd behavior I've encountered, I recommend that you thoroughly test the demo version on your system first.