As long as you have the network security code you should be able to connect any computer to your network. Once on the lan, all of you need to do is to go to the set-up for the drive of interest and share that drive. You do not have to share the drives on both computers.
If the operating system on the one computer discriminates against some of the other operating systems, hook all of the computers to the LAN and make your primary shard disk on one of the other computers.
I have two computers with Window XP. My wife routinely connects her Nook to the lan. My children have various "superior" computers which they connect to my lan all of the time.