Hi Sharon,welcome to Techzonez.As mentioned by cash site and efc you have probably got spy trojans or the blaster worm or the like.Try this free pop up stopper I found for you and of course,go to the Windows update page for up to date security.PopUpStopperClickHere

Also if you are infected and it is difficult to connect to the internet then use this link to allow connection and patch windows xp and remove the worm from your computer.SymantecWormFixClick Here

Your Windows XP operating system did not cause your problem and in itself is a good system but when you connect to the net these days you have to have a Firewall,Antivirus,and popup stopper for some peace of mind.

Come back to Techzonez and hopefully we can help you with a better XP experience.