1. A candle that was kindled as one of the Chanukkah lights but was then extinguishedwithinthe time of the mitzvah (i.e., within a half-hour) becomes forbidden and may not be used for any other purpose. Even if that candle was somehow mixed with even a thousand other ordinary candles, they all become forbidden, since the higher status of the Chanukkah candle prevents it from being nullified among the majority (Shulchan aruch and Mishnah Berurah 673).
2. However, if the Chanukkah-candle was only mixed among the other candles after the eight days of Chanukkah passed, in which case it no longer has its higher status, then it is nullified among the majority of mundane candles and they are all permissible for use (ibid.).
