open the control panel and switch to the large icons view so you have a bunch of options to choose from. Then go to administrative tools and double click on computer management. In computer management, click on disk management in the left side window. This will display all disks that are installed and which partitions are on each disk. Find whichever partition is the one that you want to shrink down and right click on it and choose shrink volume. This will shrink the partition down so you can make another one out of that. Then enter the amount of size in MB that you want to shrink the volume and click shrink. Then that size will be made unallocated space and you can choose to make another partition out of that by right clicking on it...