Let me begin by saying I have absolutely nothing against Wicca. However, just like Witnesses, many Wiccans just can't seem to research the roots of their own religion.
First of all, Wicca is by no means an old religion. It's been around only for about 50 years. A man named Gerald Gardner is credited with having popularlized the movement. You will find information about this man here - http://en.wikipedia.org/wiki/Gerald_Gardner.
Gerald Gardner was an initiate into the OTO, Ordo Templi Orientis, Aleister Crowley's pseudo-masonic lodge - http://en.wikipedia.org/wiki/Ordo_Templi_Orientis. He also claimed to have been initiated into a traditional sect of European witchcraft.
Wicca is a relatively new religion which revives and popularizes pagan practices. This doesn't detract from its validity as a path, however.
To say Wicca is an old religion is like saying that the WBTS is the same as the early church, that the Jehovah's Witnesses religion is the oldest religion on earth.
Witchcraft in general is ancient, Wicca is not.
You should also look into other "versions" of Wicca such as Dianic Witchcraft (or Wicca), Alexandrian Witchcraft (or Wicca), and British Traditional Witchcraft (or Wicca).
This might give you a good start, esp. since most Wiccans I've met have never heard about any of this, sadly, or simply refuse to hear it, they want to believe so badly that they're part of this oh so ancient religion.
As a sidenote, the popular "Wiccan rede" which is "An' it harm none, do what thou wilt" borrowed directly from Crowley's Thelema, "Do what thou Wilt shall be the whole of the Law, Love is the Law, Love under Will."
You can find more about Thelema and Witchcraft here - http://www.thelemapedia.org/index.php/Main_Page. Do a search on Wicca there and you will find much more information.
Be aware that many, many Wiccans demonize ceremonial magicians, thelema and Crowley, much as WBTS demonizes just about everything. Which I always find funny considering the modern origins. Don't let anyone else tell you what to think or believe. Do your own research and practice and it can be quite powerful.