To add a new disk to a running Windows VM

To add a new disk to a running Windows Virtual Machine

To add a new disk to Windows (2003R2, Vista, 7, 2008, 2008R2, etc) it will appear in disk manager, but it will show as 'offline' with no options to do anything. This is especially prevalent when mounting new disk on live windows machines running as VMs on VMware ESXi hosts. 

 

  1. Run the 'DISKPART' utility from any command prompt, and issue the commands:
  2. LIST DISK    (get the disk number 'n' of the new disk)
  3. SELECT DISK n     (or whatever number you got on the previous step)
  4. ONLINE DISK
  5. SELECT DISK n
  6. ATTRIBUTES DISK CLEAR READONLY
  7. CREATE PART PRIMARY
  8. Now you should be able to format and assign drive letters, etc from Windows disk manager