How to partition hard drive without formatting ...

Windows 7 and above have special ability to shrink partition and create a new one without losing any data and formatting existing partition.Before creating a new partition from old one, make sure the existing drive is 50% empty so that you don’t lose any data partition hard drive without formatting in Win7 -

Step 1: Right-click on Computer in Start menu and select Manage
Step 2: Double-click on Storage and then select Disk Management
Step 3: In this screen you see all the drives present on your computer.
Suppose you wan to partition drive D which has size of 20GB and want to create another drive G of 10GB from drive D, so right-click on drive D and select option Shrink
Step 4: In next windows, type in 10000 for 10GB in Enter the amount of space to Shrink in MB option, you can replace 10000(for 10GB) with anything else of your choice
Step 5: Click on Shrink button and wait for few minutes
Step 6: After a while, you will find a new Unallocated space which would be about same size, now right click on it and select option – New Simple Volume…
Step 7: Click next twice, if you want to continue with the same size
Step 8: Select the drive letter for the new drive and click next
Step 9: Keep the default settings i.e. Format this volume and make sure NTFS is selected
Step 10: Click next and then finish, wait for awhile and Tana! your new drive has been created without formatting any other drive

Please remember that formatting drive and creating new drive is very serious stuff which may sometimes requires patience, not going according to steps and unexpected shutdown may destroy your harddrive so be careful with this stuff.

Above was for Windows Vista and above, Windows XP user may use 3rd-party applications such as EaseUS.