How can I change my IP address on my mac? Where do I obtain it?

My Mac keeps telling me that another device has been using my IP address on the network which leads me to believe that I might be getting hacked. My computer has been acting funny lately and running slower as well which also aids in the assumption. Help?How can I change my IP address on my mac? Where do I obtain it?
You are not getting hacked, sometimes when your Mac is assigned an address, the previous one stays in the system.

Just go to your system preferences, the network control panel, then click on ';advanced'; for whichever way of connecting you are using (wireless, etc.). Then go to TCP/IP and click on ';renew DHCP lease';, you'll be given a new one.

Oh and there are no MacOS X viruses, you can't have one.How can I change my IP address on my mac? Where do I obtain it?
Your computer is plugged in(through a cable or wireless internet card) to your motem(router) Find your motem and turn it off and turn your computer off, give the motem 20 seconds and turn it back on, then turn your computer back on...

If this doesn't work, instead of the twenty seconds, when you go to bed tonight(or if you just can't get on) just turn everything off for the night(6 hours or more would be nice, could take less though).

And just because its slow doesn't mean there is a virus on it, windows computers get an average of 10,000 viruses a day; while on average Mac gets like 10 or so a year.. so don't freak out, just do whats above
Hide or change the IP address with either Peer Guardian http://www.phoenixlabs.org/pg2/ or HotSpot Shield http://www.hotspotshield.com