Please help, I have backdoor.winshell on a windows NT back office small business server system.

I searched the data base of previous questions and found one exactly like the problem I am having with one minor exception.  It can be found at the following link if it works, I am not sure I did it right.

https://www.experts-exchange.com/questions/20922773/Cannot-remove-Backdoor-Winshell-Virus.html?query=backdoor.winshell&searchType=all

The difference is I currently have windows NT as an operating system and the infected file is server.exe.  In case the link does not work, the problem is I have backdoor.winshell, it comes up on the Symantec scan.  I download the fix and run it and it says that the virus is not there.  The registries are clean but everytime I force a scan it shows up in the server.exe file.  

The previous question was not closed and was from March of this year.  I assume that the solutions provided did not work.  I followed the link to download the last solution that was given but the link was dead and it was for a more recent version of the software in any event.

Some futher information that may be helpful is that I think the person who is using this software is a previous IT employee of our firm.  As you may be able to tell I am not really an IT person, I am a hobbist who knows my way around a mother board but we have had such bad luck at our firm with IT people either leaving us or not being available when we need them that I have decided to give it a try.  Anyway I think it is a previous employee and when I go to our exchange outgoing mail queue it is filled with all kinds of spam emails that are outgoing.  As far as I know no one here activated the virus in an email.  I think it was set up previously and then activated remotely.  I am under the impression that once access was gained settings were
changed to allow regular access from a remote network, thus if the virus is ever removed the perputrator can access the network by regular means to reinstall the virus.  

I have already bought a new server with sbs 2000 on it but dont want to implement it until I am sure all the data files and all of the workstations are clear.  By the way I am currently using windows NT 4.0 all service packs with Back office small business server ver 4.5.

I would like to know;

How to close the ports allowing this entry?
If I can just delete the server.exe file and reinstall a clean copy off the original software?
How to stop remote access to my network, it is not necessary at this time?
If I cannot delete the server.exe file, how the heck to I burn this thing out.

I dont know if the following info will help but I am including it!

Scan type:  Scheduled Scan
Event:  Virus Found!
Virus name: Backdoor.Winshell
File:  C:\WINNT.SBS\system32\server.exe
Location:  C:\WINNT.SBS\system32
User:  Administrator
Action taken:  Clean failed : Quarantine failed :
Date found: Sun Feb 01 00:24:35 2004


Scan type:  Manual Scan
Event:  Virus Found!
Virus name: Backdoor.Winshell
File:  C:\WINNT.SBS\system32\server.exe
Location:  Quarantine
User:  Administrator
Action taken:  Clean failed : Quarantine succeeded :
Date found: Tue Mar 02 08:32:15 2004

Any help would be greatly appreciated, our network is being used as a spam provider and I would really like to stop it and feel safe that someone cant delete my data files at any given moment.  Thanks very much in advance!