Problems Directly connecting two computers with different OS's

My brother and I have been tring to hook up my cousins Gateway Laptop running Windows 2000 and his Gateway desktop running Window XP Home. We ran the Network Cable from both Ethernet Cards and Did everything we can to get the two computers connected. The wierd part is that my cousin had to erase everthing on the hard drive on the Desktop computer and reinstall everything. before he did that they had no problems with the network. Now when they try to play games against each other, the computers don't detect each other. Hopefully I worded this correctly, Anyone know what the problem is or how we can get it working properly. If needed I do have a spare network hub.

Is file and print sharing enabled? If your not using a hub you need to use a crossover cable, try using the networking wizard on the xp machine to create a floppy and use it on the other machine.

Have a look at the attachment here:
Basics-networking

Simple Networking of 2 PCs