A couple of things, when you direct connect over AIM then your IP is findable. I am willing to bet the same thing happens with webcams as well. TCPview I could try it out later tonight perhaps if anyone is interested in the results. During normal IMs, you are going through a server so they will not see you.

As for hiding your IP, you can look into such things as using a proxy. I believe gAIM (IM client for aim, msn, and yahoo all in one bundle) allows you to use a proxy when doing direct connects over aim.

Furthermore, even if the person only has your IP address, if you don't have a firewall up and Windows updated that they will be able to breach your computer.If you have any files on their with personal information, then they would able to find you or at least narrow their search. The firewall will deter the less experienced crackers (I hate to abuse the word hacker since it had a different meaning before the media took hold of it). A few other things worth having is a virus scanner and have it scheduled to check for updates and scan regularly.

I really do wish I had some experience about cracking so I would be better able to thoroughly explain security issues on computer systems. (I had had high hopes that the network security class this summer was going to be about that).