If you come with Windows Vista or Windows 7 and which to resize your current used disk, you may use the default disk management to resize your disk to several partitions as Windows Vista/Windows 7 do built in this functionality.
To get to this utility, run ‘diskmgmt.msc’ from your Windows Run.
In the Disk Management screen, right click the drive that you wish to resize the space.
Click on “Shrink Volume…”, enter the amount of space that you wish to shrink(where you want to use the free space).
Once done, right click to the free space and click on the extend volume, it will bring you to the extend volume wizard, enter the amount of space that you wish to extend.
Now, you may assign new drive number to your free space.