easy there guys... OP did it come with windows? do you have a certificate of authenticity on the bottom with a windows key? almost all laptops ship with an OEM version of windows that permanently belongs to the laptop and that you are entitled to install.
we of course aren't going to help you pirate it but you can do a factory restore or contact the manufacturer for restore disks if you have that windows license sticker. otherwise you'll have to buy it
WAT remover should fix it as long as its legit it doesn't matter what you use.