Create a new account, change the variable your_member_id below to the id of the new account, upload this as a new ASP page and execute it with your browser. On next login, your new account will be an admin and able to edit the original password. (I can't remember if the super admin account has any restrictions on having it's password edited by anyone else, but if it does just change the line "intAdminMemberID = 1" in config.asp to match your new ID and then change.) Remember to change the setting back and remove the admin privileges from the new account.
<!--#include file="config.asp" -->
<%
set my_Conn = Server.CreateObject("ADODB.Connection")
my_Conn.Open strConnString
strSQL = "update " & strMemberTablePrefix & "MEMBERS set M_LEVEL = 3 where MEMBER_ID = your_member_id"
my_Conn.Execute (strSQL),,adCmdText + adExecuteNoRecords
set my_Conn = Nothing
%>