In the Vital Signs workshop, we touch upon the tool SPA (Server Performance Advisor).  This unsung hero of performance evaluation deserves some love, which is why I'm writing about it over 5 years after its last update was published and made available on the downloads site, here:

 http://www.microsoft.com/downloads/details.aspx?FamilyID=61a41d78-e4aa-47b9-901b-cf85da075a73&displaylang=en

So, Clint Huffman, creator of PAL, wrote up this excellent article on how to troubleshoot server performance problems...

So, check it out here:

 http://channel9.msdn.com/Wiki/PerformanceWiki/HowToIdentifyBottleneckSPATool/

 It's the bomb, and it's free as in beer.