This is a tool that is very helpfull when troubleshooting performance problems on Exchange Servers

PAL
Ever have a performance problem, but don't know what performance counters to collect or how to analyze them? The PAL (Performance Analysis of Logs) tool is a powerful tool that reads in a performance monitor counter log and analyzes it using known thresholds.

Features

• Thresholds files for most of the major Microsoft products such as IIS, MOSS, SQL Server, BizTalk, Exchange, and Active Directory.
• An easy to use GUI interface which makes creating batch files for the PAL.ps1 script.
• A GUI editor for creating or editing your own threshold files.
• Creates an HTML based report for ease of copy/pasting into other applications.
• Analyzes performance counter logs for thresholds using thresholds that change their critieria based on the computer's role or hardware specs.

Download:
http://pal.codeplex.com/

More information about Exchange Performance Troubleshooting in an earlier post on Pro-Exchange
http://www.pro-exchange.be/blogs/exchange2007/archive/2010/04/13/exchange-server-performance-troubleshooting.aspx