Connecting two PCs

It really depends on how much money you want to spend.
If this is just for 2 home computers (like yours and a friends computer), then you can both get on the Internet, then run remote control software (like RemoteAdmin, PCAnywhere, etc) or you can set up a VPN connection between the 2 of you. That is easy, and can be very inexpensive.
Now, if this is for 2 business computers, and if you have some money, then there are more options. You can have a leased line running between both locations, with routers on either end. This can be ISDN speeds (128K), T1, T3, DS3 or even faster. Just depends on how much money you have to use on this connection.
Frame Relay connections are also a possibility. FR is cheaper than a leased line.
VPN is also an option, using existing Internet connectivity.

And don't forget, there are always modems! You can always run one system to answer a modem, and dial in from the other system.
hope this helps

The first question, is how secure do you need the connection to be?

Then, what connection options do you have?

The simplist, is just to dial up each other over the standard phone lines.

If you need the maximum security, you need a dedicatedline.
If you own contiguous property between the PCs, this is not a major problem.
You can use a "long-haul" modem, and RS-232.

Chas