FTP server problems

I just set up Windows FTP service in Win2K3, and I created a new FTP site. I want my friends to be able to access it from their home computers using their assigned usernames and passwords. I am not running Active Directory, and hopefully I dont need to.

Here's what I've done:

1) My Computer -> (right-click) Manage -> Users and Groups. I created a new Windows user for each friend and assigned it a username and password. By default, they belong to the "Users" group.

2) I created the new FTP site in IIS with User Isolation following this guide (hxxp://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechnol/windowsserver2003/proddocs/standard/wsa_ftp_isolate.asp).

Therefore, on my D: drive, I had to create a folder structure like this:

D:
-Files
---LocalUser
-----friend1
-----friend2
-----friend3

The Home Directory that I assigned to my FTP site is "d:\Files".

3) I disabled the "Allow anonymous connections" in the "Security accounts" property of the FTP site because I only want authorized access with username and password.

4) The FTP site (folder "Files" as well as all of its subfolders) has the following Permissions:
Administrators (MyComputer/Administrators)
CREATOR OWNER
INTERACTIVE
NETWORK
SYSTEM
Users (MyComputer/Users)

5) On my Linksys router, I forwarded port 21 TCP to 192.168.1.100 (which is my computer with the FTP service and IIS installed)

CURRENT SITUATION: With the above setup, I can perfectly access the FTP site via IE6 and FlashFXP (using those usernames and passwords), ON THE MACHINE RUNNING THE FTP SERVER ITSELF.

PROBLEM: However, when my friend tries to access my FTP site remotely from his computer using IE6, he gets this error message:

"FTP Folder error
An error occurred opening that folder on the FTP server. Make sure you have permissions to access that folder.
Details:
The connection with the server was reset."

When he tries to access it using FlashFXP, he gets this error:

"Data Socket Error. Connection refused.
List Error"

QUESTIONS: What am I doing wrong? I believe I set the permissions correctly. The only thing I didnt do (that was shown in that Microsoft article) was Step 4 which deals with Active Directory (There was no such "FTP User Isolation Credentials" dialog box anywhere in II6 during the setup). Also, I didnt set up Active Directory because I thought it wasnt necessary if I just want to run an FTP server.

I also tried accessing the FTP site using both passive and active options in both FlashFXP and IE. Nothing worked.

I also tried accessing the FTP site (using IE and FlashFXP) with another computer that is behind the same router as the server machine. Didnt work either.

For your info, I am running Sygate Personal Firewall on the server. But I cant access the FTP site remoting even if I turn off Sygate.

WHAT IS THE PROBLEM?????

Oh, by the way, I forgot to mention something that may or may not help in diagnosing my problem.

The very first time my friend tried to access the site using IE (ftp://ftp.mysite.com), he was able to access my files via his browser. And then he closed it. And that was it, he couldnt access it ever since. Weird.

I have created and isolation site and everything is working great; however, I want to be able to use an admin account to see each user's folder within the ftp home directory without being restricted to only my home folder. Os is Windows 2003 Server..... any suggestions?