Change IP Address

Okay, for starters, I don't know very much about computers in general, I know enough to ask semi-intelligent question. Say some random person knows my IP address. Could they use this to do to my machine remotely? If so, is it possible to change my IP address using Windows or Command Prompt? I tried doing ipconfig/release and ipcomfig/renew in command prompt, but that just gave me the same IP address info. Also, I am behind a router, if that's useful. Any help is appreciated.

Did you make sure to put a space between "ipconfig" and "/release" …?

Yes, if someone has your IP addy, then its more than a possibility someone could use it to gain access to your computer. More than likely, however, you have a dynamic IP assigned by your ISP (if you have high-speed.. then you have DHCP for sure). What I suggest you do first and foremost is post a log. Go here and download HiJiack-This and scan but do not fix anything yet. Save the scan to a log and then post results here in the Hijack This logs and problems forum.