What operating system are you using? Windows XP (Pro?), Vista
Have you already tried just creating a shared folder on one of the computers? Then, you could just map the folder to a drive letter.
Let me know if you need specific info on setting up a shared folder.
Example:
If my computer is named "MyComputer" and I share C:\BusinessDocs, then the other computer could get to that folder using the network path: \\MyComputer\BusinessDocs
Then, you could use Map Network Drive to point a drive letter, like Y:, to that folder. From then on, you would just need to type Y:\ to see the documents stored in \\MyComputer\BusinessDocs (which is actually C:\BusinessDocs on "MyComputer").
You can even map the Y: drive to the network share on your own computer (basically sharing the folder with yourself), so both computers would be the same... i.e., the documents would be accessible using Y: on both computers.