These are the bad entries you need to remove with hijack this. Do it in safe mode.
R1 - HKCU\Software\Microsoft\Internet Explorer\SearchURL,(Default) =
http://search.yahoo.com/search?p=%s
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Local Page = \blank.htm
O9 - Extra button: (no name) - {e2e2dd38-d088-4134-82b7-f2ba38496583} - %windir%\Network Diagnostic\xpnetdiag.exe (file missing)
O9 - Extra 'Tools' menuitem: @xpsp3res.dll,-20001 - {e2e2dd38-d088-4134-82b7-f2ba38496583} - %windir%\Network Diagnostic\xpnetdiag.exe (file missing)
O20 - Winlogon Notify: WRNotifier - WRLogonNTF.dll (file missing)
Run chkdsk /r from the run command