I reckon most of what happened before I was 5 or 6 is a mystery to me. I know for sure I have some memories from when I was 3-and-a-half or 4, but they are vague and there are not many of them. We moved house when I was 8 year old, and I remember a fair bit of my life before we moved, so quite a lot of what happened when I was probably 6, 7 and 8.
It also strikes me that memory is a strange thing, so sometimes, when I go back to my parents' house and we get out our old cine-8 films from my childhood, I'll find myself remembering a lot of it.... but then it occurs to me that it could be just a memory of having seen the cine film before....! So it's hard to distinguish what is a real memory and what isn't...
And it also strikes me as really strange, having twin girls who are just coming up to their seventh Birthday, is that they will not remember most of what has happened in their lives so far! The easily remember things from when they were 3 (and one of them can remember clearly some things from before her 3rd birthday), and they remember most of the major things they have done since they were 4.... but one day they will not remember much of it at all. Their lives are far more well-recorded than mine, with loads of video and photos of almost everything we do, so perhaps they will remember things better, or perhaps have even more difficulty distinguishing between real memories and recorded memories....