defrag_info1

Fragmentation is a fact of life with the Windows operating systems and although you may not know that it is a problem, slow downs in system performance can occur because of fragmentation. Files can be split into hundreds of pieces and spread out over your drive without you even knowing it. The larger the number of "pieces" or fragments the longer it takes to retrieve a file. Seeking to find the information in the file causes head movement, typically one head move for each fragment which increases latency. Fragmentation might also lead to early hard drive failure (I'm not trying to scare anyone here, I just noticed that while my co-workers hard drives were failing, mine were not). I/O performance is usually the cause of slowdowns and even though processors are getting faster and faster, hard drive throughput has not had the same kind of monumental leaps. Defragmenting your hard drive can improve I/O throughput, because the disk only needs to move one time to retrieve and entire file. This file can be read sequentially without incuring head movement, i.e. improved access times.

You should check out these links if you think you don't need defragmentation software

A tutorial : What is this thing called fragmentation?
Raxco says : Microsoft Says you need it.

Check out these sites for defragmentation. We're not advertising, but if you think their software can do a better job, then here they are. The Sysinternals PageDefrag is pretty darn cool, and our software does not defragment paging files.......
Executive Software

SysInternals PageDefrag

Perfect Disk

O&O