Windows NT change snmp community string

check out this url  
http://www.microsoft.com/technet/archive/winntas/maintain/featusability/networkm.mspx?mfr=true

The URL is better formatted, below is the excerpt.  key point is step #3
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Configuring SNMP Traps

To configure SNMP traps, follow these steps:

1. Use the steps described in the previous section, "Configuring the SNMP Agent," to access the SNMP Services.
 
2. Select the SNMP Properties Traps tab, which identifies the communities and trap destinations (see Figure 11.12).

Community names are used for authentication purposes. An SNMP agent responds to an SNMP command only if the command includes a community name of which it is aware. In other words, the community name acts as a simple password scheme.

When the Windows NT SNMP service receives a request for information that does not contain a valid community name and does not match an accepted host name for the service, the SNMP service sends an authentication-failure trap message to the trap destinations for the community name.
 
3. To add community names that the Windows NT computer knows about, enter the community name in the Community Names field and click the Add button. When the Windows NT computer sends trap messages, it includes the community name in the SNMP packet when the trap is sent. To delete a community name, highlight it and click the Remove button.

You can use any alphanumeric characters for community names. Community names are case-sensitive. All hosts typically belong to the community name _public, which is the standard name for the common community of all hosts.

 
4. In the Trap Destination box, you enter the trap destinations for a selected community name that receives trap messages. Trap destinations are specified by listing the IP address of hosts (usually SNMP Managers) that receive the trap messages by the SNMP service running on the Windows NT computer.
 
5. To enter trap destinations, highlight the community name to which you want the Windows NT computer to send traps. Next, enter the IP address or IPX address of the host in the IP Host/Address Or IPX Address field. Click the Add button to add to the list of trap destinations. To delete a trap destination from the list, highlight it and click the Remove button.
 
Regards,