here is my advice is doing netstat and find the irc server that trojan is connected to.

if your connected to that irc server be sure to note that. if its public irc network like dalnet or efnet be sure to go to #help and inform an ircop. to find an ircop just do /stats p or /who o 0 ircops always have masked hosts like 'Oper' or Net-Admin. the ircops should remove the offending 'trojan bots' channel. there usually login and remove commands. the stuff are always visible and can be read easily if you know mirc scripting well. you could understand how mirc trojans works. if you got login to the trojans. you could do !remove or !- exit or !- quit

you also should set a strong password on your NT accounts winxp is similar to win2000. winxp do have NT accounts.
just delete files from your drivers dirs.

anti-trojan programs wont help anything because people who write trojans changes files all of the time. they even used AV's and anti-trojans programs to check their files.