Most folks use the My Documents folder to keep all their personal data. Unfortunately, this folder is by default located on the C: drive, the same drive that contains the Windows operating system.
First, your personal data is very likely to be growing in size while Windows is not. In this era of multi megapixel digital photos you are in real danger of filling up your C: drive. This progessively degrades Windows performance. Sooner or later you'll fill up the disk and have to make more space by deleting some of your personal files or get into the complex and problem- fraught exercise of increasing the size of your primary disk partition.
Second, it complicates backup. Your personal data is changing all the time while the Windows operating system changes much less frequently. That means your personal data needs to be backed up more frequently than Windows. With both on the same drive you'll end up making very large drive images and having to create them more frequently as well. Similar comments apply to disk defragmentation. Mixing your personal data with Windows increases the need for defragging and results in a slower defrag.
Nope, leaving your My Documents folder on the C: drive is like storing your washing powder with your vegetables. Quite possible, but not a great idea.
Now, many folks have only a single partition of their hard drive; that is, their only hard drive is their C: drive. These folks can't move their My Documents folder. They could of course re-partition their drive but that's a complex issue I'm not going to address here.
If you do have two or more partitions on your hard drive, or if you have more than one hard drive, it's quite easy to move your My Documents folder to another drive or partition.
You will, however, need enough free space on the second drive/partition to accommodate all your documents. To find out, go to My Computer and click on View/Details and make a note of the free space available on each partition or drive. Make sure you don't get confused by your CD drive. You can't move your My Documents folder there!
While still in My Computer, right-click on My Documents and select Properties. After a few seconds you should see the folder size shown. If two figures are shown with one in brackets, note the larger figure. That's the amount of disk space you will need.
Now make a decision which drive you'd like to move the My Documents folder to. Make sure there is enough disk space. Let's say you selected the D: drive.
Click on the Start button and then right-click on My Documents and select Properties. If there's no My Documents in your start menu then right click on the My Documents icon on your desktop instead.
When you've clicked on properties, select "Move" and then navigate to your D: drive. Select the drive letter and then click "Make New Folder." Enter "My Documents" as the folder name and hit Enter and then OK. Windows will then ask you whether you want to move your documents; click Yes.
Moving your documents make take some time. Once moved, though, you can access them normally from the "My Documents" icon on the desktop or elsewhere.
In the process you'll free up a lot of room on your C: drive. Defrag the drive so it can be utilized by Windows in the most effective manner.
For more information you can consult this Microsoft document: http://support.microsoft.com/?id=310147
The ideal time to relocate the My Document folder and other system folders is when you have just bought a new PC and have yet to load your data or applications. It's something to bear in mind when you get your next PC.