Is this case Active or Passive Voice?

In order to interpret this sentence as passive voice, we have to assume there is an agent implied:

This file is located here by someone.

My guess would be that strict followers of Strunk and White would read the sentence like this, but I have my doubts about this interpretation. To locate something means that someone establishes the location, not that someone places it there.

We can read the sentence also as active, by seeing the past participle located being used attributively (used as a kind of adjective). The verb is becomes a simple copula in that case.

The sentence can be read in the same way as:

The file is big.
The file is small.

Other participles that can be used attributively are:

The file is encrypted.
The file is lost.
The file is saved.
The file is corrupted.

Although it is possible to read an implied agent in these sentences in some cases (the file may be saved by John), it is (almost) senseless to imply an agent in other cases —who cares who or what has encrypted a file, or corrupted it?

So while it is possible to read your sentence as passive, I think the common and sensible interpretation is to read it as an active voice.