Microsoft recommends users to leave 20-30GB free space for installing Windows 7. However, most of us distribute a small space for system when we installed Windows XP. Maybe consider with this situation, Microsoft added the new feature "Extend volume" in the built-in Winodws 7 Disk Management. With the help of this feature people could extend system partition in Windows 7 easily.
Right-click "My Computer"=> select "Manage" then selects "Storage" => "Disk Management". Then you could see the information of your hard drive. Here we have an example.

Our boot partition (drive C) is almost full, there's only 967MB free space left, we can not add any more data in it, such as the latest IE9 add any new Servers Patch in it. What a terrible thing. However, you could see we have a plenty free space in the secondary partition (drive D). Could we make use of this space to extend boot partition by Disk Management? Right-click drive C you may find the "Extend volume" greyed out. That's means this feature is inactivated. About this problem we must notice some rules of the Disk Management.
"Extend volume" activated-only there's some continues unallocated space behind it.
If there's not, delete the whole secondary partition behind it and make it become unallocated space
If the partition contain boot, system, page file the delete feature may greyed out
Only the unallocated space could be extended into system/boot partition. Free space is not able
As you see, there's no unallocated space behind boot partition (drive C), therefore we could only destroy the whole secondary partition (drive D), and then make it become the unallocated space. Under this way, we have to loss all of our data on drive D or back-up it before the operation. But this is also a time-waster. Is there any way could extend system/boot partition without destroy the data?
In the past people always use Partition Magic to help them resize partition. However, even though the latest version Partition Magic 8.0, it still not work on Windows 7. Now we have a new alternative which could work better than Partition Magic. Partition Assistant Professional Edition as the latest partition magic windows 7 which is a better partition software and special designed for Windows 7 users (both 32 bit and 64 bit) Ok; let's begin our tutorial about "extend system partition without losing data by Partition Assistant".
Note: Before launch Partition Assistant Pro, we highly recommend to shut down all unnecessary applications in order to make software running well.
Step1. Step1. Launch Partition Assistant Pro, right-click secondary partition (drive D) select "Resize".

Step2. In the pop-up window, drag right handle, leftwards to shrink this partition and get some unallocated space behind, then click "OK"

Step3. Right-click drive D, select "Move", in the pop-up window, put mouse on the partition when it change to cross, drag the partition rightwards. Then click "OK"

After step3, you could find the unallocated space is now behind system partition.
Step4. Select system partition (drive c) in the main interface, drag right handle on the panel, rightwards to extend system partition.

Step5. Finally, click "Apply" on the tool bar to finish our operation.

Note: If there's a step that needs to reboot system and you don't want to reboot, please check and close all live application in the partition. Undo this step, and do it again.
Only five steps, you could extend system partition on Windows 7 without destroy data, now download partition magic for windows 7 this software and then put the tutorial into practice.
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