It won't help either, other than to keep the foundation wet.
I'm amazed at the number of FReepers who are susceptible to superstition. The natural response of an intelligent person to apparitions and "messages from God" is skepticism, unless these meet the rigorous tests imposed by the Church.
All these warnings about punishment come dangerously close to equating the actions of al-Qaeda with judgments from God. Do you actually believe God is using Muslim fanatics to carry out His Divine Retribution?
Holy water is important in that it rebukes demons. St. Faustina said to use it often. I do. I believe in things other than what can be materially seen, but I didn't pour the water around my perimeter to ward of attacks from Moslems. I did it to ward off spiritual attacks on my home. I know you think I am kooky, but demons exist and they attack the faithful more than they do those who are lax in their faith.