(there can be some advanced stuff to this so if you are unfamiliar with sharing folders then you may want to seek some help

http://www.hamachi.cc/download/
you dont have to fill in the blanks, just click download
install it : ***uncheck the vulnerable windows services box, program wont work properly if you do check it***
you can follow the tutorial once it comes up (thats what i did)
Basically click on the power button on the bottom left, create a username, if you dont already have shared folders it will ask for some.
then the button next to it click it and say join or create network. (if you are lost, i would follow the tutorial)
some setting that can help:
for IMing go to prefrances and make it so it will pop the window up, or else when someone IMs you it will blink in the sys tray
play around with it, i thought it was kind of cool