you can buy all the oem you want if you go to the right places, oem generally is used by companies, but if you are building a computer you have to buy an oem os disk, well there are other ways but they cost more for a small benefit, but that doesn't matter, i really don't think your friend is as smart as he thinks he is, i think he is one of those people that had a good experience with one company and thinks it's the only way as far as gpu's, and ssd's too, and for the other stuff he is just missinformed, plug in both of your hdd's and while booting hit the instructed button to access the bios and i believe that is where the option to put them in raid will be, there is also a program in windows i believe that will do this for you, for now why don't you just ask him to assemble it and you will let us figure out the other stuff and if it works he can suck it, if it doesn't then, well it will work so that doesn't matter.