Virtual Box Appliance Drive Resize

Greetings Everyone.

I have downloaded and configured the Virtual Box Appliance of OwnCloud.
I have it setup and working, however it seems the default disk size is 50GB which is not large enough.
I tried to use the VBoxManage modifyhd command but it failed because the disk file type is vmdk and not vdi.
So how do I resize this? Or how do I make the disk type vdi?

Thanks in Advance!


as this doesn’t look like an ownCloud related question but rather a question on the usage of VirtualBox i did a short search on the internet and found various resources like the following: