You should try it. The first defrag will probably take a long time but the more you do it the faster it will take to defrag your drive. You will definitely notice a difference in performance.
Defragmenting your drive is helpful especially if you are installing or removing files on a regular basis.
One aspect that people tend to forget is the page file. Windows uses a portion of your hard drive as "ram" this is called the page file. This file gets fragmented as well BUT you cannot defrag it, it shows up as one of the "unmovable" files (marked in RED).
To do this your can use a free third party utility by Winternals. You can download the utility here
man major i thought u of all ppl would be saying that u defrag i do bout every other day or so.. im paranoid.. i update and scan my computer every other night or more.. i need a good defrag program but O&O costs so idk yet