Adware often lives inside your browser as an extension or hides in cached data.
Most pop-up "viruses" are invited in by user behavior. To stay safe:
Disclaimer: If pop-ups persist after following these steps, your system may be infected with a deeper rootkit or trojan. In this case, consult a professional IT technician.
If manual removal didn't fix the issue, you need a dedicated scanner designed for adware (standard antivirus software sometimes misses these).