Well ok, I had to throw SBS in to the title, because, well this site is about SBS.
On to the interesting part. I have always been a big fan of the Perfomance Monitoring tool since the NT days, and have got to say that now I am totally ecstatic about it in Windows Server 2008.
If you want to do a quick and dirty systems performance diagnostic on a Vista machine or Windows Server 2008 go to the Run line in Vista/WS2008 and type perfmon /report and in about a minute you will have a full snapshot of your system.
I got this from the Performance Team blog at http://blogs.technet.com/askperf/archive/2008/05/02/two-minute-drill-system-diagnostics-report.aspx When you go there dig around on their blog, these guys put out some cool stuff.
All I can say is - You Guys Rock!