Question on ASP + IIS in Windows XP

We have a local application system based on ASP + SQL Server 2000; the computer (as server) is using Windows XP, Internet Information Service.
Previously the application server was another computer using Windows Server 2000.
Now a problem: on the new server of Windows XP, users can not input new message.
But on the old Windows server 2000, users have no problem to write new message into application system.
What might be the reason? I suppose it must be due to security policy of Windows XP. So I have tried to change the security in Property of Folder, let “everyone” with “Full Control” permission. But it still doesn?t work.
So how to write into the local drive of a Windows XP machine through IIS (e.g. upload file)? Thanks.