Slow response using Remote Desktop

I am using my notebook, from outside a LAN,  to access client PCs through a Belkin router. When I am outside the LAN,  I connect using OpenVPN. Of the three clients, two work fine but the other is really slow. The response of the slow client is probably 1/50th of the other clients. For example, populating a directory in Windows Explorer takes > 1 minute on the slow client while just a second or two on the othr clients. The slow client is brand new and has a better processor and more memory (3 GB vs. 1 GB) than the other clients. My notebook and clients are running XP Pro SP3

If my notebook is inside the LAN, I don't notice the slowness. I'm not sure if this is because the LAN Bandwidth is so much more or if it is related to the VPN or something else. The slow client happens to be the client that runs the OpenVPN service.

Here is what I've done to try to resolve the problem.

1. I downloaded Qcheck and tested the throughput and response times. All clients give similar results. This was surprising to me.

2. All Remote Desktop connections are set to use "Modem (56 kbps)" even though I have a BB connection.

3. While connected, I opened task manager on the slow client and there is nothing going on. The System Idle Process is consistently > 90%

I'm not sure what I should test next. Doe sanyone have a ny suggestions? I'm out of ideas except running the openVPN service on another client and seeing if the problem moves with it. I don't think this is the problem because another computer was running the service and never had this problem.

Thanks.

-jeff