My parents still have dial up internet. I purchase them a wireless modem at Verizon, and they indicated that they were in an area that would pick up a signal. When I installed the modem, I have a very weak signal, and the computer is in the basement. What type of antenna do you suggest to get a better signal, because there is a hook up on the modem for an "external antenna" Any suggestions would be greatly appreciated.

Here's a couple you might consider

http://www.amazon.com/gp/product/B0017PJ9FY
http://www.nextag.com/adapter-antenna-external-wireless/stores-html

or make one

http://wireless.gumph.org/articles/homemadeomni.html