There are literally millions of bots running scripts out there trying to find holes in pc's. No biggie as long as you are set up right. Get yourself a firewall that doesn't return pings and they don't even know you exsist on the internet superhighway.
open up a command line and type in:
netstat -a
That'll show you all active connections
type in
nbtstat /?
that'll show you all the different options to get the host name but since you don't have rights on the ISP's domain you won't get good results but your ISP will know who it is.
Free DNS stuff here:
http://www.dnsstuff.com/