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VBoxManage.exe: error: Cannot register the hard disk 'X:\Centos64\Centos64.vdi'
{de0665e2-936b-41c5-b571-9b348d16ee54} because a hard disk '\\DiskStation\Virtua
l Machines\Centos64\Centos64.vdi' with UUID {de0665e2-936b-41c5-b571-9b348d16ee5
4} already exists
VBoxManage.exe: error: Details: code E_INVALIDARG (0x80070057), component Virtua
lBox, interface IVirtualBox, callee IUnknown
VBoxManage.exe: error: Context: "OpenMedium(Bstr(pszFilenameOrUuid).raw(), enmDe
vType, enmAccessMode, fForceNewUuidOnOpen, pMedium.asOutParam())" at line 178 of
file VBoxManageDisk.cpp

TRAyres wrote:Cannot register the hard disk 'X:\Centos64\Centos64.vdi'
{de0665e2-936b-41c5-b571-9b348d16ee54} because a hard disk '\\DiskStation\Virtua
l Machines\Centos64\Centos64.vdi' with UUID {de0665e2-936b-41c5-b571-9b348d16ee5
4} already exists

Did you move the file recently? If so, make sure you remove it from the Media Manager.

... and remember to shut VirtualBox down completely for 30 seconds or so after removing the disk, before adding it back.

ps. It is a bad idea to locate a disk outside the VM folder. Relocating the entire VM folder would have been better.