I think you can close it by going to the Control Panel and opening up the Network icon.
File and Printer sharing is probley turned on. Sometimes there will acctually be a network component installed on the pc that you should remove.
Also if you cant do it like that you can get an admin tool that will allow you to close certain ports. 139 in this case.
there is a port list file in the windows dir:
Here you go an almost complete list of ports. Have a look.
I think maybe that there aren't a limit to ports and that trojans CAN run on any port you program it to. I also think that WHOA COW, there is too many ports and trojans that can run off of them. There are so many R.A.T ports and only one of them needs to be open to run a backdoor/ trojan.