JkDefrag is good

After running CCleaner and clearing what I could from my C:, was still left with only 500MB of space there...

Then after running JkDefrag, the free space consolidated...and registered as 5GB =D

Windows Vista's defrag probably isn't working as it should...

You can get JkDefrag from here:

http://www.kessels.com/Jkdefrag/

PortableApps junkies can get it as a portable format:

http://portableapps.com/apps/utilities/jkdefrag_portable