Trace IP numbers

I've got a broadband connection at home and my PC is pretty much always online. I've also got the Norton Internet Security 2002 running. Sometimes, and lately more frequent, NIS says that there has been a attack om my PC. The attackers IP# has been logged. Is there any way of me traceing this IP#? Is this common? What should I do?

Any help much appriciated!

------------------
ADSL 2Mbit
Pentium 4 1.7GHz/Intel 850 chipset
384MB RDRAM/400MHz
60GB HDD
Elsa Gladiac 920 Geforce3
SB Live! Platinum 5.1
DVD/CD-RW
Win2k

You could start here: http://www.all-nettools.com/tools1.htm

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