From what I'm reading it looks like the XP IPX driver is no longer compatible with C&C. I think the serial cable may be the easiest way to do this for two players. My main computers don't have serial ports and are too far apart from each other, but I could use the retro gaming rig I've set up with ME together with my laptop, which has a serial port. I think I also have a really old laptop with 95 lying around somewhere. It has a Pentium 133 or something like that, but it should still be enough for C&C and the first RA.
One issue with RA is that you need the limited release 3.03 patch to play LAN games, but the no CD loader I'm using won't work with that version and you need the Aftermath CD to play multiplayer games if you have Aftermath installed. I'm not about to buy a second Aftermath CD just for this.

The older 2.00 version works fine with a null modem link though.