Microsoft Baseline Security Analyzer is a free tool which scans local or network PCs (Windows XP-8.1) for security issues.
Launch the program and you're given options to scan one or multiple computers, by name, domain or IP address(es).
If you just want to run a quick test on the current PC, click "Scan a computer" > "Start Scan".
Microsoft Baseline Security Analyzer runs a variety of checks on your system, and these can take a while to complete. Don't be surprised if you're waiting for two or three minutes.
Once it's done a full report on your system appears, with an overall verdict, and a summary of every check: missing security updates, blank/ simple/ non-expiring passwords, firewall settings, Windows update policy, Guest Account status, Administrator account details, security event auditing, unnecessary services, network shares, Registry permissions, Internet Explorer Zone configuration, SQL Server/ IIS configuration (if they're installed), and more.
Some of these items have links to explain what was scanned, and how to correct the problem.
The reports may be printed or copied to the clipboard, and they're also saved for reference later.