There is a Halacha that when one drinks wine one should dilute it first. The reason for this is that pure wine is more of an alcohol/grape syrup than it is a drinkable liquid. It is also considered disgusting to drink undiluted wine. In addition, it is interesting that Purim is based around a liquid that must be mixed, and diluted. So what is it about wine that some people drink it on Purim?
The Gemarah says that a man is obligated to drink on Purim until he can't tell the difference between cursing Haman and blessing Mordechai The Gemara says that the many parties described in the Megillah at which wine was drunk, helped contribute to the Nes of Purim. These include the party with Vashti, the party at which Esther showed Haman's plot to Achashverosh, and others. This is the source of the obligation to drink wine on Purim.
So, how big is this quantity of wine that must be drunk? According to some opinions, one should drink a little bit and then take a nap because when one is sleeping he won't know the difference between the two statements. Others say that since "Arur Haman" has a gematria of 502 and "Baruch IMordechai" has the same gematria, one should drink until one can no longer add up the numbers that reach the gematria (i.e. l,2,3..502). Either way, why is it that men are so stringent with this particular Halacha, namely, that one should drink until he doesn't know which way is up, while women usually seem to disregard this halachah? Perhaps one reason that women seem to disregard this halachah is that women are not supposed to drink. If women are not supposed to drink "ad deloh yadah," then why not?
Coming back to the question of why one has to drink something that must be mixed, there is a gematria that since both Yayin (wine) and Sode (secret) are equal to 70, when we drink wine, our secrets are revealed. When people get drunk they say everything that they know. In addition, they will not remember having told their secrets.
The shoresh, the root word, of the name Esther means "hidden", because Esther had to stay hidden. She was told not to tell of herself to others, not of her parents, not of her friends, not of anything. People were certainly trying to find out where she came from, where she was born, and other things about her, but she kept the secret. Therefore, Esther could not drink, lest she give away her secret. Nowadays, why can't women drink? What secret are they holding?
In Sefer Bereshis we are told of two different things that are hidden and preserved. One is the light that was created on the first day that was saved for the tzaddikim to enjoy in yemos hamashiach. The second was the Levyasan, a huge fish. Hashem had made one male Levyasan and one female Levyasan. Seeing that both together would destroy the rest of the world, Hashem killed the male, cut it up, salted it, and hid it with the light that was to be enjoyed by the tzaddikim when mashiach comes. So what do these two things have in common? They both pertain to the geulah. The geulah is also something that is hidden.
The Gemara in Chulin says that one can find Haman in the Torah. Let us go back to creation where the first hidden thing is revealed. After Adam and Chavah ate from the Etz HaDa'at, Hashem asked Adam, Ayekah - where are you? Many times I have heard that Ayekah refers to Aichah. What does Aichah speak about? It speaks about the Golus and the destruction. Hashem is saying: all you have to do is tell me what actually happened, and all will be fine. However, an improper answer can lead to golus. "Hamin Haetz ...," - did you eat from the tree? Hamin is spelled with the same Hebrew letters as the name Haman. Adam thought that Hashem really didn't know whether or not he had eaten. So instead of lying completely, he blamed it on Chavah, and as soon as everyone started blaming everything on everyone else, they received a punishment of golus (they were thrown out of the Garden of Eden). There is a Machlokes over the type of tree the Tree of Knowledge was. One opinion holds that it was a grape vine, and as we said before, drinking wine causes hidden things to be revealed. Adam and Chava drank wine and they realized they were naked.
Returning to ad delo yadah, men must drink until they look at "arur Haman" in the Megillah and can't tell whether it is really "Arur Haman" or "Baruch Mordechai." Women don't have this obligation. Why? I'll give you two examples, one that pertains to a month from now, Pesach, and the other that pertains to now, Purim. In Mitzrayim, where both the men and women were slaves, why was it that the women had to convince the men to allow them to reproduce? The work was hard enough for the women, and they wished to add to this by becoming pregnant? Furthermore, why did the women even think of bringing another person into the back-breaking slavery of Mitzrayim? It was because women, in the depths of Arur Haman, saw the Baruch Mordechai. They knew that they needed a new generation of children in order to be saved. The same thing happened by Purim. It seemed as though the Jews were about to be destroyed, but Esther saw the Geulah. Men have to drink until the secret becomes clear to them, that these things are not constructive, but destructive. As a last note, the Megillah doesn't end with everyone living happily ever after, with a great redemption. Rather, it ends like it begins. The Jews were mixed throughout 127 provinces, still in Golus, because the geula was taking place one step at a time.