In Disk Management, just delete all volumes one by one and then the dynamic disk can be turned into the basic disk.
Please do the following steps,
Method 1: Use Windows Disk Management to Convert
Step 1. Run diskmgmt.msc to load Disk Management directly, or you can right-click "My Computer/This PC", select "Manage" - "Storage" - "Disk Management".
Step 2. Right-click on a dynamic volume and choose Delete Volume… Continue deleting volumes until the whole hard disk displays as Unallocated.
Step 3. Depending on the operating system you are using, after the deletions, the dynamic disk will become basic disk automatically; or you still need to right-click the dynamic disk and then choose
If still facing the problem then go to method 2.
Method 2: Use Command Prompt to Convert
Run Command Prompt as administrator. Then in the command prompt window, type these commands successively:
*diskpart
*list disk
*select disk n (n is the number of the dynamic disk you want to convert)
*detail disk
*select volume n (n is the number of the selected volume)
*delete volume (If there is more than 1 volume, just delete them one by one until all volumes on the disk are removed.)
*select disk n
*convert basic
I think it will solve your problem. dynamic disk to basic disk
What you mentioned above will erase all their data. If I'm not mistaken, I think people here is trying to reverse from "Dynamic Disk" back to "Basic" in the form of preserving their data.