Can i know how can we differentiate clients installed SEP wheather how many desktop or laptop?
it's base on your database.
Embedded database support 5000 client.
Microsoft SQL Server can support up to 50,000 clients. If your organization has more than 50,000 clients, you can install another management server
About choosing a database type
http://www.symantec.com/business/support/index?page=content&id=HOWTO55329
See chetan comments
Embedded database supports 5000 clients per SEPM.
SQL database supports 80,000 clients per SEPM for SEP 12.1. In SEP 11.x version it's 50,000 clients per SEPM
https://www-secure.symantec.com/connect/forums/sepm-embedded-database#comment-8904671