The issue is not the baptism, but what you believe. If youbelieve in Jesus as the savior, and the Trinity, then you are fullyChristian even if you had been born Jewish (though you could laterrenounce that and return to Judaism).If you believe in Judaism and do not believe in Christianity (orother religions), you are Jewish (though you would also need aformal conversion to Judaism if you had not been born Jewish).A Jew who underwent baptism but does not believe in Christianityhas not changed from being Jewish just because of that ceremonyalone.Other informationJudaism does not proselytize or seek converts, but it doesaccept sincere converts.Conversion is a life-changing and very serious undertaking and apotential convert should think it over carefully. It must not bedone on a whim or because of temporary circumstances. One whoconverts is expected (from then on) to live as a Jew.The first step would be, without outside help or influence, toget to know about Judaism. The person who felt interested shouldhang around a Jewish community in order to get a sense of whetherJews and Judaism as it is actually lived appeal to him/her. Also todo some reading. English-language books on Jewish thought and lifecan be found in Hebrew bookstores.After that, the interested person would approach a Rabbi and askabout enrolling in a relevant formal course of study. This can lastfor several years and is an integral part of the process, sincehe/she will have to actually practice the religion.Once that is completed, the convert immerses in a mikveh (ritualimmersion); and, for uncircumcised males, undergoescircumcision.