Slow Installation

My Vista install is slow. I mean REALLY slow. I do take care of it, scanning for viruses, spyware, defragging, and constantly using CCleaner. Over a time period of about nine months, however, it has become indescribably slow. It hardly has anything starting up at boot (AVG, along with the copy of Internet Download Manager that I use), is a fairly new system (a Sager NP8660 laptop), and is completely virus and spyware free (went through several programs confirming this). I have, however, tried out a lot of programs in my time, and I fear that the leftovers of these installations may be clogging up my system. CCleaner is only good for so much, I'm assuming. Are there any other tools that I can use to unclog my system and cut the hard drive thrashing? This, and/or relative tips for a healthy and clean Vista install.