Rearm windows 8 Enterprise Evaluation to Extend Trial Version another 90 days

type this command: slmgr /rearm

Type command : slmgr /dli  to check current license

Type command:  slmgr /dlv to check detailed information about Current license type

Type command:  slmgr /xpr to check expiry date of current license.

http://www.alltechtricks.com/2013/03/rearm-windows-8-extend-trail-version.html