Different network speed between XP and W2K with Win2003 Server + DC

Hi,

We have the following situation:

Server:
Windows 2003 Standard + Domain Controller

Application:
based on a Foxpro DB, installed on the Server.

Workstations:
6 XP SP2 + 1 W2K. Each of them has a network drive mapped to the place where
the application is installed. The application is called via a shortcut
pointing to an EXE which is on the server.

Problem:
When a user performs a query in the application, the result is displayed
immediately on the W2K workstation. on XP, it takes about 3 seconds (before
I do some tuning, it was 7 seconds).

Is it a fact that W2K is faster in such a situation or is there something
still wrong on the XP workstations?

Thanks for your answers.
Hubert.