When we get a brand new computer with the OEM Windows 7 OS, we always find that the vendors had partitioned hard drive already. However, most users are not satisfied with the unreasonable partition so that they have to repartition hard drive by themselves. There are two situations:
Situation A: Only one partition contains the System, boot, and other data.
Situation B: A small system partition with two large data partition
In situation "A" people need to shrink the only partition by the built-in Disk Management at first then create other partitions. You could read more details about "Create New partition in Windows 7" Through this way we could repartition hard drive.
In situation "B" if you want to create more partitions when you need you will receive the error message as below:
This error message is caused by the shortage of Disk Management in Windows 7. As we know one hard drive could contain maximum four partitions-three primary partition with one extended partition. However, it doesn't like other OS, when you create partition there's two options: create "primary partition" or "extend partition". In Windows 7 all of this becomes automatic. You could only create primary partition before three partitions existing. Therefore, when the partition is setting up there's no way to repartition hard drive in Windows 7 unless format hard drive. To solve this problem we could only repartition hard drive through resize partition.
There are several ways to resize partition. The built-in Disk Management and the Disk Part.exe (a DOS command) could help you do some simple partition resize operation. Unfortunate, there're a lot of limitations on them. It can not work as well as you wish (to learn more details about "windows 7 disk management") therefore more and more people prefer to use partition manager to help them manage their hard drive. Aomei Partition Assistant Professional Edition is the latest Windows 7 partition manager which is specially designed for Windows 7 users. It could support both 32 bit/64 bit and Windows 7 SP1. Resize partition is just an ice of berg of this partition software.
Follow the steps of the tutorials you could easily repartition hard drive in Windows 7 without formatting HDD. download partition magic for windows 7 this Windows 7 partition manager.