What was your study plan before you took the test? If you think you're weak all around on the Quantitative, buy all of the Manhattan Quantitative books. I think there are 3 or 4 of them. Those books break it down step by step. The Kaplan 800 book also focuses on tough problems. Working through these tough problems will help you get all of the easy questions right, most of the intermediate ones, and some of the hard ones. That should boost you significantly from a 25%
Hope that helps,
Jeff