We Have 100 User CAL, So How I can Install it on Exchange server 2010 with windows 2008 R2?

Just keep it with you for records so you can show these at time of audit and all. No need to put it in sevrer and there is no option where you can place this into server.Anil

Anil is right, you don't need to install them. But make sure you have them for licensing purposes. And you can find more information about the CAL: Go to Organizational Healty->View legal information regarding the CAL. By the way, for license query, I would suggest you phone Microsoft directly. In the United States, call (800) 426-9400 to speak to a Microsoft representative. In Canada, call (877) 568-2495. More information: On-Premise Licensing for Exchange Server 2010 http://www.microsoft.com/exchange/2010/en/us/Licensing.aspx#ExCalComFrank Wang