OK, the title of this post is slightly misleading as it may not be 10GB for you. But the following method is definately one worth doing to see how much space you can claim back from the Windows OS (as it already takes far too much).

There's a feature on your PC (if you have XP or Vista) called "System Restore". This allows you to roll your PC back to a previous state if you screw something up. Now by default, the System Restore feature uses 12% (!) of the total space on your drive to save restore point files and settings. If you use the standard settings, XP creates a restore point every day. The actual size of a restore point varies but using the standard settings, your PC could be holding data on 200 system restore points, which you don't really need.

Now you can easily reduce that System Restore space to just 1GB on your hard-drive which all you will ever need. When you do so, XP will delete the rest of the data and give you the space back. Plus in the future, System Restore points will only use up that 1GB of space.

Since I am using a German language PC, it is pointless to make screenshots if you don't understand German, so just do this : go to Control Panel then System then System Restore. Now using your mouse, slide that slider to the left until you get to around 1000MB (1GB) of space. This should be either 1% or 2%. When done, click the "apply" button to save the changes then "OK".

Now how much space did you get back? I got 10GB!