^^^ that isn't true. All my computers interact with each other and I have had various operating systems but not run Ubuntu and Windows 7. All you need is for each computer to understand the communication system that was designed. The bitness, OS, or any other factors do not matter if the software is implemented.
I use Samba on my Ubuntu computers to share files with my Windows PCs.
anyways, for a simple network, just use the link provided above.