If it say's it's for sytem builders, It's for system builders. If you're not one or aren't building a new Computer, then don't use it. If you do you are breaking the EULA terms. you can activate it once but if you reformat or change the mobo, It might be hard to activate it again as you have to phone microsoft and if you can't prove to them you are a PC builder them you are stuffed. So if I was you, buy a retail version.