Windows PC Defender is a new rogue from the same family as OmegaAntivir (new interface), Windows Additional Guard, Windows Guard Pro, Ultimate System Guard, Smart Virus Eliminator, Windows Protection Suite, Windows System Suite, Windows Security Suite, Malware Destructor 2009, FastAntivirus, MalwareCatcher, VirusShield, Extra Antivirus, Virus Sweeper, Ultra Antivir 2009, Virusdoctor, VirusMelt, VirusAlarm.
It comes from fake online scanners. Detects inexistent infections to scare user, pushing them into buying a license.
Thanks to Jaxryley
BleepingComputer Windows PC Defender removal guide.