>>>and if you don't have the sticker then you don't have a licensed copy of windows
Well I have built a number of PCs and bought the OEM versions of Windows but never stuck the sticker on my PC so it is not totally true to say that.
If a PC was bought off a company like Dell or HP then it should have a sticker, and if you bought it from a local PC builder it should also have a sticker, but there are probably many PCs around with NO sticker, but their Windows is still legal.