First, disable opportunistic locking on the server. See mskb #296264 on how to do that.
Second, make sure that anti-viruses on server and workstation do not check VFP files (.DBF, .CDX, .FPT).

>
>
>Server: Windows Server 2003
>Client: Widnows XP
>Application: Visual FoxPro9 SP1
>
>Where are one user the performance is good.
>
>Where another users open the application, the performance decreases very user by user.