There is a piece of software called Belarc Advisor that can spec out your PC super-quick and seems incredibly helpful. Unlike Magic Jelly Bean Keyfinder, which is a good tool to have as well, Belarc Advisor not only gets the keys for various pieces of Windows Software, but also checks out the status of your (Windows-only) machine’s security hotfixens and displays your system specfications.
It does this all in a web browser and then gives you links to where each piece of software it finds is installed.
About the only downsides I can find are that this isn’t free software and it doesn’t display licenses for game software.
I suppose neither is surprising coming from a business-oriented services company, but oh well.