How to convert vdi to qcow2

1. Change directory to c:\Program Files\Oracle\VirtualBox

2. Execute a command "VBoxManage.exe list hdds" and you will carefully look the "UUID"

UUID:           63ce53eb-7d0c-4634-9920-7f6e30529fed

Parent UUID:    base

State:          created

Type:           normal (base)

Location:       E:\VMs\WIN-7\WIN-7.vdi

Storage format: VDI

Capacity:       25600 MBytes

Encryption:     disabled

3. Execute a command

c:\Program Files\Oracle\VirtualBox>VBoxManage.exe clonehd 63ce53eb-7d0c-4634-9920-7f6e30529fed E:\VMs\WIN-7\win7.qcow2 --format qcow2