Use ALter database with Modify file option to move the tempdb database and do an instance restart.

FOllowing links would be helpful.

http://www.sqlservercentral.com/articles/Administration/63568/

http://support.microsoft.com/kb/187824

or in BOL

ms-help://MS.SQLCC.v9/MS.SQLSVR.v9.en/udb9/html/72bb62ee-9602-4f71-be51-c466c1670878.htm