IPsec is a wonderful technology for identifying computers and securing the exchange of data between them. I've written and spoken extensively about in the past. It is, however, a bit of a challenge to configure, especially if you're newly learning about it. Microsoft recently released a diagnostic tool to help you create and test your policies. It checks for common network problems on host machines and suggests repair commands. It collects IPsec policy information on systems and parses IPsec logs to deduce why a failure might have happened. Beyond IPsec, it offers trace collection for VPN, NAP client, Windows Firewall, Group policy updates, Wireless, and System events. The tool's diagnostic report derives its conclusions from the system logs collected by the tool during its analysis phase, which are sufficient to diagnose any network related issue. For further assistance, you can share the logs with network administrators or Microsoft support.
Get the tool here: http://www.microsoft.com/downloads/details.aspx?FamilyID=1d4c292c-7998-42e4-8786-789c7b457881&displaylang=en
It works on these versions of Windows: