Yeah, most people wouldn't know how to look, even if you just formatted it, but its best to be sure.
Anywya, i say the same thing. Get a new system
If its cheaper, get another one from a company, but if you want the best performance/price, i'd build one using custom parts, or buy them, and get a mate to build it or something. That way, your getting the best PC for money can buy, and no un-upgradeable parts.
Plus, because your not a gamer, you don't need a good video card, so you could spend more on what matters to editing people, more memory, or better sound, since you do sound editing as well.