As suggested use
Dropbox if the computers isn't on the same network (or in the same house) as the other ones.
If you're in the same house/network, I'd suggest that you share a windows folder and just choose that folder as the chat logging one.
That way you don't need other software, but if you leave the house, it wont work unless your connected to your network.
Windows XP
http://www.microsoft.com/windowsxp/using/networking/default.mspx
Windows Vista
http://windows.microsoft.com/en-US/windows-vista/...-up-a-home-network
Windows 7
http://windows.microsoft.com/en-US/windows7/Add-a...puter-to-a-network
/ 
