More importantly, is this a recent development or has it been going on for a while? The solution could be as simple as using HijackThis to stop programs from loading at boot time to reinstalling a clean version of your OS -- or a dozen things in between. We just need more information to help.
msconfig for windows. Disable all the programs you dont need during boot, they will start later when you need them. That is what I did, now my laptop boots pretty quickly. I dont know how to do it with other OS.