Two computers with same IP

[Satbir Hundal]

I have a network (two computers) behind 2Wire DSL Router with dynamic IP to
access broadband Internet. One machine is Win2000 and one is WinXP. I need to
connect both these from my remote third computer that is Vista. Problem is
both Win200 and WinXP are showing same IP address 75.x.x.x when mouse is
hovered over the no-ip icon in the systray. Internal addresses are different,
192.168.1.64 on Win2000, and 192.168.1.65 on WinXP. But these separate
internal IPs are useless to me if I want to connect remotely from my Vista
machine that is not physically connected. I have configured the 2Wire router
to port forward Win2000 as following:
VNC1 Port 5501
VNC2 Port 5801
VNC3 Port 5901

I have also configured the 2Wire router to port forward WinXP as following:

VNC1 Port 5500

VNC2 Port 5800

VNC3 Port 5900

How can I make Win2000 and WinXP get different IPs starting with 75.x.x.x
without paying for static IP(s) that do not start with 192.x.x.x so I can
access these using VNC remotely from my Vista?