something acessing internet

Hi, can someone please tell me how to find out what is accessing the internet on my computor?

I am in the country, so am using dial-up connection.

Every time I boot my system, some thing connects on me.

I have run multiple virus-malware scans, but none seem to be present.

Is there some way I can find out what program or service is doing it?

I would be greatfull for any help on this

Thanx

Dan B.