One of the best ways to ensure that your PC is safe and secure is to keep all your installed software up to date. In some cases, applications will update themselves automatically, or alert you when a new version is available. But many apps don't. And even if they do, we often dismiss the alert box because it's not convenient.
Patch My PC is a utility that scans your computer for dozens of well-known programs, both free and commercial, and alerts you if they need updating. It'll even apply the updates for you, if you wish.
The program is available as a paid-for commercial product, but there's also a very functional free version too. You can download it from http://patchmypc.net/download. It works on Windows XP and above, is only a 0.5 MB download, and is free of malware according to VirusTotal. It's portable too, so just run the downloaded file and you'll instantly get a report such as the one below.
You can then allow the program to download and install patches. Or, if you wish, you can make a note of the updates it claims to have found and then source the latest updates yourself from the software vendors' own sites.
Patch My PC. My thanks to Richard Miller for telling me about this great program.