Maybe you're asking for too much: Keep online forms as brief as possible

Whether it's because people always seem to be in a hurry on the Web, or because they're reluctant to give personal information when they think it might generate spam, it is generally true that the longer the web form you ask people to fill out, the fewer the people who will fill it out. Bob Johnson elaborates on this topic in his blog post Online inquiry forms... a special place for brevity.