I have a desktop running WindowsXP, with two Realsys network cards. One card allows me to go online. The other card, untill recently allowed me to go online with my laptop, running WindowsME. At My Network Places, the XP shows both cards, working perfectly, and with ipconfig, both cards show up. I can ping 192.168.0.230 that the ipconfig shows, and 192.168.0.200 wich the laptops winipcfg shows. However, when I go to the laptop, I can't ping the desktops IP Address.
The automatic setup for the laptop was so wrong, I had to set it manually.

My first impression is that your laptop card could be going. If you haven't made any recent system changes, this could be the most likely variable.

Just to double check, the IP for your card in the XP machine is 192.168.0.230, and the laptops is 192.168.0.200?
And when you have established a connection from the XP machine to the laptop, you are able to ping the laptop from the XP machine, but cannot ping from the laptop to the XP machine.

Could you give some more information on how you have your settings? I'm looking for default connection speed, host settings, etc.
The problem could be that the laptop got confused about how fast its supposed to send data, or where its supposed to send it to.

were you ever able to ping the desktop from the laptop before. when you do ipconfig on the laptop or winipcfg what is the gateway and what is it on the desktop