I've visited the SysInternals site a few times over the course of my career because of some strange problem that I just couldn't track down. The amount of information about what is actually happening on your system that the SysInternals tools provide is phenomenal. The site was run by Mark Russinovich and Bryce Cogswell until they got hired by Microsoft. However, the tools are still available and being updated, only now they are hosted by Microsoft themselves.
So, today's tip is to visit the SysInternals page on Microsoft's TechNet site and familiarise yourself with what is available. You might find that one day it will save you hours of frustration.