file sharing with MR814 from outside the network

I'm relatively inexperienced at networking and have a question about
access to files from outside my home network.

Previously, I ran a home network through a little netgear hub. Each
computer had its own IP address, so I could easily access any shared
folders from any internet-enabled computer through the standard
\\xxx.xxx.xxx.xx/FOLDER_NAME means. (Sorry, I don't even know what
this access protocol is called.)

Now I've switched to an ISP that allows me only 1 IP address and have
switched my home network to run through a Netgear MR814. I have no
problem sharing files inside the network, but I'd really love to be
able to access files from outside as well. Obviously, if I simply try
the protocol mentioned above (i.e., just using my IP address, I'm
attempting to connect to the router, not a PC on the network). Is
there any way to get through the router to one of the PCs running on
the network?

Specifications:
-the PC I want to access runs Win2KPro
-the one from which I'm trying to access that PC runs XPPro
-I have set the router up to reserve IP addresses for the PCs inside
the network
-The internal IP address for the PC that I'd like to reach is
192.168.0.4

Thanks for any help.

Mitch Davis