Try and see if this is helpful:: http://www.italki.com/answers/question/82433.htm

Past Perfect Form : Had + past participle example : i Had eaten my dinner before she arrived i (Had) + (eaten) my dinner before she arrived ...................... when we use it : to express about event had finished ............................... Positive form : You had studied English before you moved to New York. Negative form : You had not studied English before you moved to New York Question : Had you studied English before you moved to New York? .......................................... some words that come with Past Participle: already - for - by the time - when - after - before .......................... other examples: Examples: I had never seen such a beautiful beach before I went to Kauai. I did not have any money because I had lost my wallet. Tony knew Istanbul so well because he had visited the city several times. Had Susan ever studied Thai before she moved to Thailand? She only understood the movie because she had read the book. Kristine had never been to an opera before last night. We were not able to get a hotel room because we had not booked in advance. A: Had you ever visited the U.S. before your trip in 2006? B: Yes, I had been to the U.S. once before.

Peachy and sonia had a pretty good explanation a few days ago. Let me see if I can go find it for you...

past perfect (had done) the past perfect is 'had + past participle' (gone, seen, finished etc) sometimes we talk about things that happened in the past: she arrived at the party. this is the starting point of the story. then, if we want to talk about things that happened before this time, we use the past perfect (had...): when she arrived at the party, paul had already gone home.

Past Perfect Form [had + past participle] The Past Perfect expresses the idea that something occurred before another action in the past. It can also show that something happened before a specific time in the past. Example: You had studied English before you moved to New York