If you want to log all the commands that you are executing in Exchange 2007 management shell to eventviewer, use the below registry key. As a result of this, all the commands you are executing from Exchange Shell will be logged to eventviewer and you can refer them whenever you want. This way we can keep track of what changes we are doing on day-to-day basis.
set-itemproperty HKLM:SOFTWAREMicrosoftPowerShell1PowerShellSnapInsMicrosoft.Exchange.Management.PowerShell.Admin -Name
LogpipelineExecutionDetails -value 1