Local area network

It will greatly simplify thing is you just get a router and do things that way.

If you've set up the LAN and your computers won't talk, it's becuase they're designed not to.

If you want to be able to acess the information on both computers from either one. Right click on the Start menu or go to My Computer. Right-click on the drives/folders you want to share.
Go to the properties of the drives or folders you want to share. When you tell the pc's to share with another computer, windows will have you use another wizard to share things through a LAN, but it's pretty quick and easy.
When you're done on one computer, it will have you save the wizard to a disk to run on the other pc. That part's pretty easy too.

If both computers can't access the internet, then you will need to get a router. Connect the cable modem to the router, then the CPUs to the router. The input and output ethernet ports are clearly labeled on whatever router you buy.

When you get everything worked out, you can also set up some user accounts and share a calendar, among other things, through microsoft outlook. Once you've got the connection set up, the rest is just up to your preference as to what you want the computers to do. You can set permissions on folders/files so only one person, or both, can access any given folder/file. That will also add another layer of security to those folders/files to prevent unwanted intrusions.

Good luck.