My IP address had changed?

I have scanned my pc with many anti-virus, sites and firewall. My mcafee anti-virus is telling me that there is someone on my network (his ip is my ip that i had before). And all sites are indicating a new IP for my pc. So how can I have it back?

My IP address had changed?adware remover

You could try setting up a static IP. A static IP is an IP which never changes. Normally, a router assigns your computer a new IP address every time you log on to the internet. There's a great tutorial for setting up Static IPs at http://portforward.com/networking/static...

Hope this helps.

My IP address had changed?antivirus protection

Your external IP address (the one visible over the internet) is assigned by your Internet Service Provider. You don't have any control over it.
well actually ip addresses update every day so if you have your modem off for 24 hours your modem will be pinged and see that its turned off so you wont get the ip u normally get then when u turn it back on after 24 hours you will have a different ip :D just to let you know.....
it depends....if its for home what Internet Service Providers(at%26t,comcast,verizon)they lease you an ip address sometimes for days weeks or months and when that lease is up they will give you another ip address.or if you have 2 or more computers hooked up they will sometimes give 2 computers the same ip by mistake.or if you have a wireless network in your house someone might be acessing your router to get free internet access though you...if so to fix that just give your router a password.