+1 for JKDefrag
ScanDefrag is a nice GUI for JKDefrag
EDIT: it had a fast option which only defrags the files that are worth defragging. this should be perfect for what you want.
I have to say thanks for you dudes who recommended JK defrag, I've seen it a few times while browsing online, but I've always thought it was too hard to use, well I was wrong.
I installed it on my mom's laptop with Vista Home Premium last night and it reclaimed about 5GB of space, then today, I installed it on a pc with Vista ultimate and it reclaimed about 10GB of space, just by it's optimizing tecniques!
Really really cool little program, I don't like the Scandefrag GUI that much, but I do love this one:
http://www.emro.nl/freeware/
A short guide to set up Jkdefrag, go to this link and download the Jkdefrag zip file:
http://www.kessels.com/JkDefrag/index.html
Extract it on a folder where you'd like to keep it, then download the GUI from the site above
http://www.emro.nl/freeware/ extract those files in the same folder and open the GUI file, then you just set the options in the GUI, you can even create shortcuts to it, schedule a task to let it run once a week and so on.
Really really great app, much much better and way faster than any other commercial software out there
