Defragment the file system

When you initially write a file to disk, it's stored in one contiguous mass, but as you edit the file, the file can become fragmented (that is, pieces are stored in non-adjacent spots). As you can imagine, it takes longer to open a fragmented file than an unfragmented one, because the hard disk's read and write head must hop around on the disk, picking up the pieces of the file. That's why defragmenting a hard disk improves its performance. By rearranging the files stored on it so that each file is stored in a contiguous area, defragmenting a hard disk improves performance immensely.
NOTE: Defragmenting takes a long time, so make certain you have enough time. If you choose to defragment while you are at your desk, don't use your computer while it's being defragmented, because every time the content of the hard disk changes, it has to start all over again. Disable your screensaver and anti virus program before running the defragmenter to minimize restarts due to hard disk changes.
To defragment a disk:
1). Select Start >> All Programs, Accessories >> System Tools >> Disk Defragmenter. The Disk Defragmenter dialog box will appear.
2). Select the drive you want to defragment, and then do one of the following:
Click Defragment to start defragmenting the drive now.
Click Analyze to check how badly the drive needs to be defragmented.
If you do the second, a recommendation appears after a minute or two. From there, you can select whether to defragment or not.