How to get rid of pop-up ads?

You've probably got malware, and a lot of that's not going to show up on standard virus scans. Time to call in the big(ger) guns. Contact a local computer store and ask them to help you, or even try a local computer club (there might be a few listed in your area on MeetUp). I hesitate to give you removal instructions as those can often be complicated and they are generally dependent on what you've got.

You can fight back against pop-up ads but make sure that your browser configured correctly, having the latest version or even changing to a new one.
What you don't know ;
* Chrome doesn't block pop-up ads from showing.
* Your homepage, startup page or search engine has changed to a site you don't recognize.
* Unfamiliar extensions or tool bars are added to Chrome
* The Chrome desktop shortcut opens an unfamiliar website
* These changes may be caused by malicious software known as malware.

First at all, check what anti-virus company runs in your computer.

For example, <<you have Comcast and by such, you have installed Norton Anti-virus.

First you run Norton Anti-virus. Of course this step won't do much. But it is required, so you call Comcast and said what you have tried.

From here, Comcast will help.

You don't need to download third party software, you don't need to take your computer to anywhere.

Comcast service includes the removal of all kind of virus and malware.

The expert will ask you if you want to follow his instructions or, if you want to let him control your computer and he will fix the problem while you watch in the screen what he is doing, while he might explain his steps by phone.

You will notice that they do have the proper software and experience to repair your computer from outside attacks.>>

If you have other company for internet services, and this company includes anti-virus services, then call your company and they will take care of the problem. If you have an Anti-virus company that is not affiliated to your internet service company, then you may be charged for the service.

Don't waste money paying third parties that will do the same repairs that your internet service/anti-virus company will provide for free, because such services must be included in the Anti-virus contract.

And, do not download "free" software online that promises to fix your problem. Remember, nothing is free in this world, and these websites will install their own malware in your computer. Watch out.

There are a few malware removal and protection softwares out there. Some of them have free versions for home use. Malwarebytes is one I have used in the past.
The newer versions of Windows (7 and 8) are supposed to have protection built in.

Microsoft offers this tool.
https://www.microsoft.com/security/pc-security/malware-removal.aspx

Here are some older directions on how to use malwarebytes
http://www.pcworld.com/article/243818/how_to_remove_malware_from_your_windows_pc.html