so i'm about to embark on my first ever system build, have all the parts ready to assemble and ready to go, but i think i've run into a problem. i bought and opened what i thought was windows 7 home premium, and it seems that i in fact purchased the upgrade kit as apposed to the full version. since i have opened it i can not return it, with that said, is there a way to make it work? should i just call microsoft and see what they can do? please help, i really don't want to take a loss on this!