In tip 0085, we described this problem and a solution.
If tip 0085 doesn't work for you, try the following:
1. Rename %SystemRoot%\Help\Update.cnt to %SystemRoot%\Help\Update.old.
2. Delete %SystemRoot%\System32\Windows.gid (Normally hidden).
NOTE: If %SystemRoot%\System32\Windows.gid is not present, it will be recreated by your next search.
You should now be able to use Find in Help.
NOTE: On your next reboot, you may delete %SystemRoot%\Help\Update.old.