waree,
I read a "PC World" article on this subject just a year or so ago, where they took a series of junked-up, fragmented hard drives and first did a de-junking (using CCleaner), a registry cleaning (I can't remember the program they used but it wasn't JV16), and then a defragmentation (using Windows' built-in defragmentor). After each process, they rechecked the times of various computer functions like start-up, specific application boots, and various downloads. They found a 5%-15% improvement in speed for each of the three clean-ups they performed (depending on the computer and the severity of the problems); thus, they were able to effect about a 15%-45% improvement in overall performance by cleaning the registry, degunking the HD, and defragmenting it. In general, most users probably wouldn't notice a profound difference in performance, but even a 15% improvement is worth the trouble. And since clutter accumulates over time, slowing down a computer incrementally as it goes along, like dust collecting on an an automobile, a cleaning now and then can't hurt, esp. when things like JV16 Power Tools and CCleaner are so cheap or even free.
