Open Terminal, go the directory where your virtual machine files(old vid files and the new vdi file just created) are and type: VBoxManage clonehd OldVidFile.vdi newDynamicallyExpandingVidFile.vdi -existing The clone process should begin and you should see output similar to this: Attach the new dynamically expending VDI and extend the Windows volume In order to do this, We need to use the VBoxManage clonehd command. We need to transfer the Windows system installed on the old VDI file to the new virtual disk image We just created. Use clonehd to 'copy' old VDI to the new VDI file (in my case:Win7X64.vdi) you just created Here, I choose 60GB for the maximum storage size and 'Win7X64.vdi' as the file name. Choose VDI file location and specify the maximum size for this VDI, If you specify 60GB as the maximum size, then maximum windows disk space will be 60GB.In 'Create New Virtual Disk Wizard' choose 'Dynamically expanding storage'.Open VirtualBox (VB), choose menu File–>Virtual Media Manager.Create a new dynamically expending Virtual Disk Image (VDI) using virtualBox Mac It it actually much easier than I thought. Here is how I changed the Fixed-sized Windows 7 Virtualbox VDI from 20GB to a dynamically expanding VDI file. This afternoon, When there was only 20MB space left in Windows system, I finally decided to try to expand the disk size of Windows volume. It didn't take long before Windows started alerting me there is not enough space for update and paging. I chose to create VirtualBox VDI file of fixed-size storage of 20GB. I made a bad decision when creating the Windows virtual machine (VM). 6 months ago, I Installed Windows 7 on my Mac using VirtualBox.

Download windows 7 for mac virtualbox