How to Clone Hard Disk?
Why do you need to clone hard disk?
Hard disk clone means copying the contents of one hard disk to another disk. It is useful for large enterprises to provide new computers with a standard set of applications. You may use disk cloning to upgrade old disk to a new one or replace the slow hard disk with the faster SSD (Solid State Drive). Also, disk cloning is a way of backing up system and data. If you want to have a copy of a lot of files or folders which are luckily all on the same disk and you do not want to back up them one by one, you surely should clone the whole disk in one time. It saves the time of select each file or folder and copies it; it is also easier and avoids you with repeated boring work.
Without knowing the function of disk clone, I did suffer the tedious and tiresome work before. That happened when I just entered college and had my own PC. In order to avoid data loss due to my wrong operation since I was not familiar with using computer then, I decided to backup all the things on d disk to my USB flash drive. Then, I copied the files and folders one by one. Though there were not too many matters on d disk for I had not used my PC for too long, it still took me almost a whole morning to finish the work. Besides, some files and applications copied by the "Copy" and "Paste" functions in right menu cannot be used. Had I know the service of disk clone then, I would not foolishly to do the repeated work. Now, with the help of Partition Assistant, it is much easier and faster. This software even allows me to clone HDD from large disk to smaller. Then, how to clone disk with AOMEI Partition Assistant? Please follow the text please follow the below text.
Step by step guide to clone hard drive to another disk
To follow this guide, please download AOMEI Partition Assistant Professional (Windows 10, 8/8.1, 7, XP, and Vista supported) to have a try.
Step1. Install and launch AOMEI Partition Assistant. Right click the source hard disk (here is Disk 1) you want to copy and select "Copy Disk" in the drop-down menu. To clone only system drive to new disk, for example, move Windows 7 to SSD, please select “Migrate OS to SSD” instead.
Step2. In the pop-up window, AOMEI Partition Assistant provides you with two methods for cloning hard disk: "Copy Disk Quickly" which only copies the used space of the disk. "Sector-by-Sector Copy" which will copy all sectors of the disk no matter whether it is used or not. Then click "Next" to continue(here we will take "Copy Disk Quickly" for example).
Step3. In next window, select the destination disk to put the data of source disk on, and then click "Next". When you choose the target disk, please pay attention to its size; make sure that its size is not less than the size of the data you are going to copy, at least equal to the latter. 
Tips:
You can tick "Optimize the performance of SSD" to improve the reading and writing speed of SSD if the selected destination disk is a SSD storage.
If there are partitions on the destination disk, they will be deleted. Therefore, if these data are useful for you, please make a backup of them with AOMEI Backupper.
Step4. In this window, this program allows you to adjust the partition size on the destination disk. There are three options for you: “Copy without resizing partition”, “Fit partition to entire disk” and “Edit partition on this disk”. After finishing the adjustment, please click "Next". 
Step5. You can preview the disk cloning operating by viewing the "Pending Operations". To commit the "Pending Operations", please click "Apply". 
As for "Sector-by-Sector Copy", the detail steps are very similar to that of "Copy Disk Quickly". The only two parts that are different are step 2 and 3. In step2, you should select “Sector-by-Sector Copy” as the copy method; in step3, you should make sure that the size of the destination disk is no less than the size of the source disk according to the principle of the way of copy, no matter how less the used space is in the source disk. The rest operation is just the same as what described for "Copy Disk Quickly".
Note:
If the hard disk you want to clone contains system boot partition, the operation will be completed under the "PreOS Mode". Do not worry about that you don’t know how to get into PreOS Mode to operate, because Partition Assistant will help you; the only thing you have to do is to follow it.
To copy hard disk or migrate OS from GPT disk to MBR, the limitation of MBR partition style should be taken into consideration. MBR supports up to four primary partitions and no bigger than 2TB.
The deleted or lost files can only be copied to the destination hard disk through “Sector-by-Sector Copy” method.
In addition to hard disk clone, AOMEI Partition Assistant also provides "Partition Copy Wizard" for cloning a specific partition.
Dynamic disk, Offline disks could not be set as target disk.