I also turned off "Move large files to end of drive... (all sizes & other set to default)" and increased speed dramatically.
My system:
windows7 64bit
6gb ram
i7 920 @ 3.0
hdd that was used is WD VelociRaptor 150GB 10000RPM SATA-II 16MB Cache
Used space: 117GB
Free space: 22GB
No operating system installed on it, hdd just being used for games
Defraggler version v1.17.172 (64 bit)