You may be loading a bunch of unnecessary apps at startup.
Go to Start\Programs\Startup & check out the items in there. Everything in that folder loads when you boot up. Good place to clean stuff up.
Also, check out the icons in your Systray (bottom right corner)......if there is anything there that you don't need-each item usually has an option to remove it from Systray. That will also speed things up bit.
Beyond that, I'd say to run the standard virus & spyware checks, and may defragment your drive once or twice.