About DNS

Hi,
I have W2k Adv. Server with active directory installed.I created one zone in DNS i.e. shopping.com my Name Server is w2kserver.abc.com.When i ping shopping.com then it’s gives me unknown host.I configured this shopping.com in IIS.When my client gives shopping.com then it don’t open the site,but when they give www.shopping.com then it works.I want when my users write shopping.com or www.shopping.com then site will open.
I would appreciate if someone gives me assistance on it.
With regards.
Anurag.