Using VirtualBox to resize a virtual disk

Recently I needed to resize the C drive on a Windows 2008 R2 virtual machine from its existing 10GB to 20GB.

I performed the following steps using VirtualBox v4.

1. Execute from the command prompt (Note the Virtual Machine was Powered Off)
VBoxManage modifyhd C:\VM_Test_Env\Servers\W2K8R2-04.vdi --resize 20480

2. Start the virtual machine.

3. In Disk Management – right click the C drive – select Extend Volume – follow the Wizard prompts.

You should end up with a larger C drive.