You can play either. However you wont be able to go to the new expansion areas of Frontiers without this disk. But the original EQOA will work, you also wont be able to accumulate class mastery points or go past level 50. So I would suggest just starting out on Frontiers if you havent started anything at all. It has all the new graphics, cms, and expansion areas. Nice new things (some yucky ugly things like elf robes =0(..LOL ) to look at and go to. So hope this helps. Good Luck!!