Everytime I come on the net at some point and sometimes more than once my firewall tells me that a Net BIOS Session tried to enter my computer...

I am not very familiar with computers or the internet.

I went to DNS on two of these occasions to trace the IP address that came with the alert...and one was a intenet provider in Sault Lake City ( 66.219.229.250 ) and the other was an internet provider in Los Angeles ( 216.70.236.200 )...it did not tell me who the last numbers applied to...

I am not on a network, local or otherwise, this is a home/office personal computer

My questions are:

1. is this common for these sessions to come up?
2. should I allow access?
3. if it's not common then why is this happening?
4. and how can I either stop it or track the culprits responsible?

I am running Windows 2000 Pro service pack 4, with AVG free edition, Adware SE, Spyware Blaster, and a Zone Alarm firewall...80GB...384MB Ram...I don't know really what specs you need.

Total computer experience about six months...internet about three months.

Thanks !!!