I've been using VMWare for a while and am very happy with it, but I would like to compare it with VirtualBox. Apparently the disk images are compatible, and I have successfully booted my Fedora based VM created by VMWare in VirtualBox... but the network is completely unavailable. How do you port a virtual machine from VMWare to VirtualBox and keep all the capabilities intact?
have you tried going into the options in virtual box and changing the network adapter to the VB one? VB is a bit different in it's virtual adapters, you might have to create a new one attached to the nic and then specify that one as the primary nic.
If the network is unavailable, you may want to check your VirtualBox configuration and make sure you have a network card configured. If you do, then the next stop would be the OS running in the virtual machine. An unfortunate fact of some operating systems is that they don't always appreciate hardware changes. If the OS is not auto-detecting the change to the network card, you may need to reconfigure it to support the new card.
Another possibility is that you were using a fixed IP address. VirtualBox uses a couple of schemes for networking that are a bit different than VMWare. You may need to change the IP inside the VM to match the expected subnet.
Outside the VM, you need to use either a bridged networking device or configure ports virtual ports through the NAT system if you want to gain access to your Virtual Machine.