You need to remove following Windows registry keys using "regedit.exe" tool.
Before removing these, please create backup of registry.
And note that I cannot guarantee if you get any problem.
HKEY_CLASSES_ROOT\Directory\shellex\ContextMenuHandlers\TortoiseHgCMenu
HKEY_CLASSES_ROOT\Directory\Background\shellex\ContextMenuHandlers\TortoiseHgCMenu
HKEY_CLASSES_ROOT\Drive\shellex\ContextMenuHandlers\TortoiseHgCMenu
HKEY_CLASSES_ROOT\Folder\shellex\ContextMenuHandlers\TortoiseHgCMenu
HKEY_CLASSES_ROOT\*\shellex\ContextMenuHandlers\TortoiseHgCMenu
HKEY_CLASSES_ROOT\InternetShortcut\shellex\ContextMenuHandlers\TortoiseHgCMenu
HKEY_CLASSES_ROOT\lnkfile\shellex\ContextMenuHandlers\TortoiseHgCMenu