Sounds like you're in a pickle, because like TC123 has stated, it's like you're already locked into the "friend zone", and once you're painted with that brush, it's pretty hard to wash off. I guess the real dilemma, is what you do next. There's a few scenarios that play out in my mind, as I read this.
The first scenario, is that you keep being there, gaining her trust, and continue being the friend etc etc, as Marmelade suggested. I wouldn't drop the L word just yet either, as rjg20 has suggested; that's too much of a leap of faith. But if you don't know where you stand, and where she stands, then you're setting yourself up for a bit of heartbreak. Does she really know that you like her? Or are you assuming that she knows that you like her?
If it's the first one, then you're really in a pickle, because a) She knows the score and b) She's not doing anything about it. She's either stringing you on, by not shooting you down or telling you where she stands in it all (either she likes you back, or not), or she really is ignorant of how to deal with a situation like that. If she knows where you stand, ask her about it.
If it's the second one, where you're just assuming that she knows that you like her, then it's not so bad, because there's nothing out in the open just yet. i.e her doing nothing about it, is great, because she doesn't know anything about it. Problem is, you'll have to bring it up, if you want something to come from it.
The second scenario is that you throw it all down, and let it out. I wouldn't call it a confrontation, but I would bring it up casually (if there's such a thing of raising this topic casually). Tell her that you like her, and you don't want to be in the friend zone anymore. Clearly state that you don't want to just get into her pants, but want to build a long lasting relationship. If she says something like, 'But you're like all the other guys, and are just saying that to get into my pants', then clearly, you've already lost the battle, because it's already been a year, and she still thinks you're like that; talk about having your work cut out for you.
If she still thinks like this about you, then clearly she doesn't know anything about you (I'm currently assuming what you want is a long lasting relationship, and not a trophy lay, and just seeking approval by asking this question, without all of the full details). Plus, you're probably wasting your time, because you've already been painted with the "bad guy / every other guy" brush, and that paint is sticking...
Tough call, but it's a make or break situation. You're either going to win out, and start a relationship, or you're going to lose out, by either just being the 'guy friend' for a fair while, or you're not going to be friends at all.