In Regedit:
HKEY_CURRENT_USERSoftwareMicrosoftVisualStudio[Version Number}Find
Remove all keys that starts with Find and Replace, like Find1, Find2, Replace1, etc. You can remove history for Findonly or Replace only, or remove only particular Find…
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.…