Here is what I had to do to get rdesktop to connect to XP Professional installed on VMware Workstation 6 running on Feisty.

In the guest XP system added a password for my account and turned on Remote Desktop in the System control panel applet on the Remote tab.

I edited /etc/vmware/vmnet8/nat/nat.conf and added the line

3389 = 192.168.72.128:3389

in the [incomingtcp] section.

Then I edited /etc/systl.conf to change the IPv4 forwarding line:

# Uncomment the next line to enable packet forwarding for IPv4 net.ipv4.conf.default.forwarding=1

Then I rebooted.

Now I started VMware and activated the guest XP system. Now the command:

rdesktop localhost

Works as expected.