Belarc Advisor is a powerful system information tool that provides genuinely useful details on every aspect of your PC.
The program doesn't just tell you how much RAM you've got installed, for instance: it also reports the size of each individual memory stick, and tells you if you've any RAM slots free, very helpful if you're planning a memory upgrade (and much easier than opening your case to take a look). Other hardware-related information listed on the report include your CPU type, motherboard model, BIOS date, and graphics card details.
Belarc Advisor runs some handy security checks, too. It'll check to make sure you've antivirus protection installed, for example, that it's up-to-date and real-time protection is enabled. And the program will also list all your installed Microsoft security patches, and warn you if any are missing.
The report on your installed applications is particularly useful, as it uses icons to highlight programs that haven't been used for a very long time (perhaps more than a year). If you notice apps you're no longer using, and you're sure will not be needed again, then uninstall them to free up hard drive space and maybe a few other system resources.
But our favourite part of the Belarc Advisor report has to be the Software Licences section, where the program displays the licence keys for many popular applications (Adobe, CyberLink, Electronic Arts, Microsoft, Nero, and many other companies are supposed). Print out the report, and keep it safe: if you lose the original CDs for an app then these details will save you a lot of hassle, and maybe even money.