plz help!

If someone is mucking around with your computer because they have your ip address is there anyway that you can stop them even if you don't have their ip address. I think i know who it is and im only worried because it is not my computer. If theres a way to help me pleaseeeeeeeee!!!!!!!! they have only done it once but i dont want to risk them doing anything when my mum is on. HELP!

Well, you can always get a new IP address. In case you don't, use a firewall. Even old ZoneAlarm([url]www.zonelabs.com[/url] - trial version) may do the trick.
You may also want to be sure that your computer doesn't contain any trojans or spyware. Plus, don't chat or mail the person, it is another way to ***** your IP.