As Dereck said it won't be an issue as long as they are both on the same controller chip but really is there any point? The pair likely won't run much faster and you will add a minute or more to your boot time. I think, esp if your sata3 ssd is 400mb/s or faster, that you are better off suing them as individual drives with the sata3 as the boot & some programs drive and the sata2 as a data & less frequent programs. This way you still get fast boot times and 120gb total storage. All you need to do is pay attention to where you install programs to (C: or D:).