Pre-installed VDI?

[gert7]

Is it possible to borrow someone else's installed VDI file if I'm having problems installing?

[maro]

It's not clear to me whether the VDI file you mention contains
    (1) a TC (or MC) installation from someone else or
    (2) whether you are using TC as the host and want to test the 'virtualbox-ose.tcz' extension.

Either way it should be no problem to take a virtual disk image (e.g. a VDI file) from someone else and create a VM on your system with it. I personally do this all the time, e.g. I create a disk image on a Linux host and copy it to a friend's system who then runs the same emulator (or virtualizer) on a Windows host. If you are careful and know what you are doing you can even migrate an image from one product to another one (and I mean not just to convert the disk file format). But there are limits to this and it very much depends on the individual circumstances.

What you have to be careful about when taking a virtual disk from one host to another one is to ensure that the (virtual) hardware configuration of the source and the destination VM are at best identical. Since the release of version 4.0.x of VirtualBox this should now be much easier as one could just copy the respective *.vbox file. But as the handling of those files requires a bit of more advanced knowledge, the probably better advice would be to visually compare (using the VirtualBox management GUI) the settings of both source and destination VM and ensure that they are aligned.