ffdshow is just a simple directshow mpeg4 asp video decoder. It won't and it can't bring down the whole windows. If you have trouble it very likely you delete some system files yourself, or your display driver is faulty.
The only active component inside is "FFDSHOW.AX" . Manually type "regsvr32 /u ffdshow.ax" then ffdhsow is gone........ no longer registered.