Share VirtualBox VDI between computers over network

I have been working inside a Windows7 virtual machine using VirtualBox installed on my Windows7 OS on my primary PC. I would like to share that VM on my home network so that I can access the same VM on any of my PCs without moving or copying the VDI file. I will only be accessing this VM from one machine at a time.

So far I have installed VirtualBox on my 2nd PC (running Windows7 as well), created a new VM on that PC, and tried to attach the the shared VDI file to it through the network...but I get the following error:

Failed to open the hard disk \win7.vdi.

Cannot register the hard disk '\win7.vdi' {699d9a41-515d-4123-bac4-f0fb8f5e7601} because a hard disk '\win7.vdi' with UUID {699d9a41-515d-4123-bac4-f0fb8f5e7601} already exists.

Result Code: E_INVALIDARG (0x80070057)
Component: VirtualBox
Interface: IVirtualBox {3b2f08eb-b810-4715-bee0-bb06b9880ad2}
Callee RC: VBOX_E_OBJECT_NOT_FOUND (0x80BB0001)

The same error is produced if I try to associate the VDI file to the VM on my main PC through the network, such as:

\\COMPUTERNAME\C\VMS\win7.vdi

The VDI file is not dynamic and no snapshot has been taken/used to my knowledge.

I hope this is possible and I simply have the syntax for a networked vdi wrong. Any help would be greatly appreciated!

This article may help. It discusses sharing between different OSes, but seems like it might work in your case. I was just about to try it out when I found your question.