Here are some links on how to make use of performance counters in .NET code:

http://msdn2.microsoft.com/en-us/library/ms979204.aspx
http://www.codeproject.com/dotnet/perfcounter.asp
http://www.codeproject.com/vb/net/PerformanceCounterUtils.asp
http://www.codeproject.com/system/cpuusage.asp

Jeffrey Kelly
http://sailwhatcom.com