Not Seeing Any Wireless Networks on a XPS 420 - Antenna Needed?

I have a dumb question:  Do I need an antenna for my Dell XPS 420 wireless network adapter, and if so where do I connect it into the machine?

Problem:  My Dell XPS420 cannot see any wireless networks unless the wireless router / access point is located within a few feet of the machine.  When the access point is within a few feet of the machine, then I can see the wireless network and connect with no problem.

Details:  Machine is a Dell XPS 420 with an internal Broadcom 802.11g Network Adapter running MS Vista.  As I mentioned, the wireless adapter works fine as long as the access point is within about 3 feet of the PC.  All troubleshooting steps indicate that the Broadcom wireless network adapter is enabled and working with no problems. 

My assumption is that I need some type of antenna to boost the range.  Is that assumption correct?  If yes, then I need to know where on the PC to plug the antenna in (like I said, a dumb question :-).

Thanks!