Symptoms

1. You perform disk cloning under Windows. Cloning succeeds without errors
2. The clone/destination disk disappears from Windows Explorer
   

   Disks before cloning C: to H:	Disks after cloning C: to H:

   Drive letters disappear only when cloning is done in running Windows, and without reboot request. Drive letters do not disappear if cloning is performed using Acronis Bootable Media, or if cloning, initially started in Windows, required computer to reboot to complete to operation.

Cause

This is by design. Disk is hidden to keep it as close to the original as possible. Windows does not allow having two disks with identical drive letter in the system at the same time.

Solution

If you cloned the disk to be able to quickly switch to the clone, if anything goes wrong with the first disk, then no action from you is required. When you want to switch to the clone, select it in the BIOS/UEFI boot menu. All the drive letters will remain untouched as they were on the original disk.

If you need to access files and folders in the clone, assign a drive letter to it using Windows Disk Management.

1. Go to Start -> Search -> type diskmgmt.msc and double-click on diskmgmt in search results

2. Windows Disk Management window opens

3. Locate the cloned disk and select the partition that you need to access. Right-click on the partition without a letter and select Change drive letter and paths...

(!) Do not assign a letter to System Reserved partition if you have such partition on the clone.

4. Click Add

5. Select a letter for your drive in Assign the following drive letter and click OK

(!) Assigning a letter to the partition will not break the bootability of the system on that disk

6. After a letter is assigned to partition, it will appear in Windows Explorer and you can access files and folders on it.