In windows NT and 2000 it's Microsoft SMB software that is accessing the ports. This allows for network print/file sharing through client software such as Samba. The problem is that it also allows access through Trojans to your file system. It's very easy to use these ports for outside access. So the best thing to do is close the ports off then see if there's any adverse affect, if not you're okay. Try a firewall such as ZoneAlarm to stop any in/out access.
If you want to monitor things have a look at:
http://www.commodon.com/threat/threat-detect.htm