In Regedit:
For SQL Server 2005 :
HKEY_CURRENT_USER\Software\Microsoft\Microsoft SQL Server\90\Tools\Shell\Find
For SQL Server 2008 :
HKEY_CURRENT_USER\Software\Microsoft\Microsoft SQL Server\100\Tools\Shell\Find
For SQL Server 2012 :
HKEY_CURRENT_USER\Software\Microsoft\SQL Server Management Studio\11.0\Find
Remove the Find and Replace items.