UltraVNC

Anyone have an idea how to enable RDP on windows 2000 pro?

I know it's possible (they use exactly same kernel) I did it once, but it wasn't really clean solution...

If you have any linux/unix machine acting as a NAT, then you probably don't need encryption at all. Alll you need is to start ssh, with port forwarding. All communication is encrypted, and it also helps avoiding too restrictive firewalls.