Ancient Ruins & Advanced Technology?

[tbontob]

What is the difference between ancient ruins and advanced technology on a planet?

Would I be correct in assuming that ancient ruins are a source of "found" or "ancient" technology and that advanced technology is technology which we would normally research?

And can anyone give a "guestimate" of the probability of technology actually being found on the site?

What kinds of ancient technology is "findable"? And is any of the ancient technology actually useful and if so...why?

For example, Massive Engine Destroying Weapons are not very useful when compared with our normal ionic dispersers.