Follow these steps-
First of all disconnect all the networks including Internet and LAN.
Step 1- Download any random removing adware program of your choice.
Step 2- RE-Open PC/Laptop in Safe Mode.
Step 3– Using Adware removing program perform a complete system scan.
Step 4- It will show list of malicious adwares in the list, select which you want to remove or select them all and remove them.
Reboot your system and there you go!!
I recommend bitdefender adware remover software!!!
Note: the above method is working and all the adwares will be removed after the Step 4. Still the Ads is showing up on your PC then try to install antivirus softwares like Avg, Avast etc (Avg is the one i recommend) it will scan all the files one by one not affecting your personal data and remove it completely. But if you don’t want to install antivirus because of losing of some .exe extension files like installed games, keygens, valuable softwares etc then formatting your existing windows is the last step left after that. Just backup your data’s from the c drive and go for it.