How to resize a partition in Windows Vista. As we all know by now when we wanted to resize a partion in Windows XP we have to download or buy a utlitiy do do so.Now with Windows Vista it is included in the operating system. Click start and click on Control Panel,in the Control Panel search box type in partition. Click on Create and format hard disk partitions. Disk management should appear. Click on the partition you want to shrink and select Shrink Volume. In the dialog box you need to enter the amount you want to shrink the hard drisk volume by,not the new volume you are trying to create. If the partition you want to shrink is 50 gig and you want to shrink that volume by 10 gig,enter 10000 in the appropriate box. Then click Shrink button. Extend a Partition.. In the Disk Management screen, just right-click on the partition that you want to shrink, and select "Extend Volume" from the menu. On this screen, you can specify the amount that you want to increase the partition by. In this case 50GB size that it was before.