When I had my MacBook, it took forever to boot, forever to even show the apple logo. What fixed the problem for me was disk utility. I repaired permissions, then I clicked verify disk. It told me there were some errors, so I threw in my os x disc and booted from it by holding "c" at startup. I then went back to disk utility and clicked repair disk. Problem fixed.
Maybe you can give this a shot, let me know how it goes.
Maybe you can give this a shot, let me know how it goes.