You Have 1 Unclaimed Prize ads might occur when your computer is infected with a malicious browser extension installed by Adware or Potentially Unwanted Software (PUPs). The ads that says “You Have 1 Unclaimed Prize” are caused by adware. The domain is only used to promote the ads and not malicious or associated with the malware.
The ads might vary, sometimes it promotes products from different shopping sites, sometimes fake updates and in this case a so called prize you won. Related adware is usually bundled with freeware. It’s very important that you pay attention to the license agreements and installation screen when installing free software. If the custom installation offers a decline, custom or advanced button, click it to find out if there is any additional software installed that you do not need or want.
During installation the adware offers you additional software to enrich your browser experience. Take note that this additional software might be bundled with ads to keep it free.