How can I configure an employee's home vista laptop to connect to his work PC on our private network?

I have a user at the company that I work at that needs to have access to his work PC from his house.  Instead of buying a brand new laptop or configuring a used one our of own, we decided to just buy a copy of pcAnywhere and install it on his work PC and his personal laptop at his house.  He brought in his personal laptop, so I have that in my possesion.  

His laptop has Windows Vista installed on it, which will work with pcAnywhere.  His work PC has Windows XP installed on it.  His home laptop is not part of our domain or anything (nor would we want it to be) but his work PC is part of our company's domain.  His laptop is going to be connecting from behind a router (most likely a little Linksys or Belkin personal router) but his work PC is behind our Netscreen-25 firewall.

I have installed the pcAnywhere software on both the laptop and the work PC.  The laptop will be the remote client and the work PC will be the host.  The work PC has a static IP address.

How do I configure his personal laptop so that he can connect to his work PC?  I know how to create a "New Connection" on his laptop (to tell it to connect to a host) but I'm not sure what to put in for the IP address.  His work IP address is a 192.168... address (we're class C) but on his end that could be a computer at his house...  I read the book that it came with (and I do mean BOOK) and it says:

"If the host computer is on a private network, use the IP address of the router.  The host's administrator must configure the router to allow the connection."

So... I have to add our company's router's IP address as the host?  I understand that, but is that really needed?  I couldn't even guess on how I would confiure our router but I could do the firewall part (I don't believe our router does any blocking or anything... I think it's all done at our firewall.  Our router is just a small Cisco 1700 series that is where our internet comes in through but no one has ever had to touch that, just the firewall whenever we need to configure something).  

I'm assuming that I'll have to configure my firewall to allow this connection but here's the thing...  We have another user at the company that has the same exact setup EXCEPT we gave her a laptop, so she's not using her personal laptop.  The laptop that we gave her was Win XP Pro (same as her work PC) and the laptop that we gave her was in the same domain as her work PC (our company's 1 and only domain).  So why would I have to configure my firewall?  As you can see I'm quite confused but I'm hoping that someone out there has been in the same situation.
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Don't forget that his home router may need to be configured as well...
You would need a VPN to do this safely. No VPN and your system is wide open to hackers or misuse from others. In my opinion this isn't worth the hassle to set something like this up for just one user. There are services like logmein that provide secure connections to PC's the logmein client is running on, and there is no need change anything in the setup of your routers. Logmein has a free version, and also paid versions which have more functions. They also have "hamachi" which is free and can be used to transfer files between both locations. I suggest you try that first.

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setup the PC at home to connect to the companies external IP address. this is the one the  router has. You then need to setup the firewall at the company to port foward. here is a list of ports

So on the firewall you would say what is coming in on *portnumber* foward to ip address work computer IP. all should work. Like clarktr2 said depending on his home router that may need configuration also put that would porably just need to allow outgoing and incoming connections on the proper port numbers
Swamp_ThingAuthor Commented:
I went with the "logmein" service and it's very simple (and cheap!).  I just purchased a single license for 1 year and it only cost $39.99... Symantec pcAnywhere was $180... I could use for 4 years before it would start to be more than pcAnywhere and even then I would most likely need to spend another $180 or so because the software will be 4 years old.
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