I assume you're using Internet Explorer? Go to
www.panicware.com and download the free version of Pop-Up Stopper. It's a small program and very effective. You might also want to check your system for adware/spyware. You can also get Ad-Aware 6.0 for free at
www.lavasoftusa.com. It can find all kinds of advertising nasties crawling around on your computer. If your daughter's been browsing and clicking on things indiscriminately, you've certainly acquired a few.
In addition to your antivirus, it's not a bad idea to have a trojan detector/cleaner. I use The Cleaner (
www.moosoft.com); it's free to try for 30 days, then I think it's $29.95. Well worth every penny. There are other anti-trojan programs, such as Tauscan (
www.agnitum.com) that are very effective and inexpensive. Check out
www.wilders.org for some good security program info.
If your daughter does any file sharing or chatting via IRC, there's an exceptionally high possibility of having picked up a trojan, and your antivirus might not pick it up. Trojans usually give someone else access to your computer and/or sensitive files, such as your passwords.
Are you running a firewall?
