How do I connect to another computer (screenshare/capture) on Mac OS X 10.5?

I want to connect to another computer and control it with my mouse and keyboard. The thing is, my computer is on a network and I want to connect to another computer that is on another network. I am confused because (for example) a linksys router starts of as 192.168.1.1 and all other clients are 192.168.1.xxx (the "xxx" replaced by numbers). What IP Address do I type in to connect to the other computer to connect directly to it?

In the example below, I want to connect to the computer on the IP 10.0.1.17 (the computer's IP that is on a network) with the public IP 76.4.105.131 (from the internet service provider) while I am on a different network.

What do I type in, some sort of combination of the two?

IP Address (Public, External or WAN IP Address)
76.4.105.131

Internal IP Address (LAN or Router IP Address)
10.0.1.17

Step by step instructions please. Any help would be great.

p.s. This will be a Mac-to-Mac connection, both running Mac OS X 10.5 Leopard.

If they were both on the same network I would simply type in 76.4.105.131 but I'm confused because of the different networks issue.

Are you saying you want to control your computer at home - from outside, say at work? The easiest way is to use a program like teamviewer
TeamViewer - Free Remote Access and Remote Desktop Sharing over the Internet

Otherwise you would have to do something fancy like portforward through ssh - but check out team viewer and reply back if it is what you want.

Thanks. It's exactly what I needed. How many times can I connect using the free non-corporate edition? Is it unlimited?

Just curious:
How can I set up the screen capture/control feature that 10.5 and 10.6 has?

It is free for personal use. It will remind you every now and then - I find it unobtrusive.

Just curious:
How can I set up the screen capture/control feature that 10.5 and 10.6 has?

Click to expand...

I'm not sure what you are asking but here is a pretty decent tutorial on screen sharing
Leopard Makes It Easy to Share Your Mac's Screen Locally and Over the Internet
But I don't agree with how he portforwards everything - it is unencrypted and insecure. I highly recommend ignoring the port forward advice in the article. It is in my opinion, very dangerous to open known insecure ports as he has.

Here is another tutorial that talks about ssh port forwarding - which is how I access my internal network.
Tutorial: Screen Sharing in Leopard (Mac OS X 10.5): How it works and how it doesn't | MacFixIt - CNET Reviews

If that isn't what you are looking for please let post exactly what you are looking for.