Defragment your hard drive – yes, do it on a regular basis.
Why? Because in time pieces of files are stored physically scattered on your hard disk. So, everytime your hard drive gets to read a file, it has to work more to find and read it. Defrag finds all the files pieces and moves them all together so that each file is stored in one place contiguously. This process will speed up your hard drive.
In order to perform this operation you can either use the integrated Windows defragmentation or use a third party application. I suggest you to go for O&O Defrag 14.