But it says i have to activate windows but i checked and i cant because it says its unlicensed and i really dont want to buy windows again because this annoying watermark while working
Replacing the motherboard could be showing Microsoft it is a different computer, probably the biggest change one can make that will not activate without a phone call to Microsoft.
The key word for me that sets of a big red flag is the OP mention of the "watermark". No legit copy has that.
I have recently, change a couple of motherboards. As it happens, they were Dells. These were pre licenced with Microsoft, by Dell. There was documentation with them, should the activation go wrong, including a new, licenced, key. After installation they were already activated. I agree with Bass. There should not be a watermark. The OP can sort out the problem with a quick call to the MS facility.
Hey guys thanks that (some of) you were trying to help me but for some reason its just gone so i guess thats going for me