Windows 7 does not come with USB 3.0 controller drivers. It will display error during installation and won’t find driver using Windows Update.
Intel USB 3.0 eXtensible Host Controller Driver needs to be installed. But it is no longer available for download. You can download it using Internet Archive or use a backup link below.
You may get the following error when importing existing image to the VirtualBox:
A hard disk with UUID {e9758c99-e50c-41c7-877f-f03c1454d136} or with the same properties (‘image.vhd’) is already registered.
This happens when you make copy of a virtual image and want to add it to VirtualBox, but the original image is also registered. To change the UUID use the VBoxManage utility installed with VirtualBox.
VBoxManage.exe internalcommands sethduuid image.vhd
I don’t have any of the VMware products installed on my PC, but I have some VMDK virtual machine disks which I run inside VirtualBox.I had trouble installing some update on one of my virtual machines because I did not have enough space. I needed to make it larger, but I was not able to find some easy solution without having to install VMware Server or similar robust not free software.
I used to copy virtual disks using CloneVDI tool and I realized that it is possible to resize the virtual machine disk during cloning. This tool is very simple to use and does not require to be installed.
You can download it from VirtualBox forums or you can download it from my site mirror.
To tell the truth it is not migrating at all. VirtualBox – virtualization software developed by Oracle – has ability to work with multiple types of virtual hard disks including VMDK (developed by VMware) and VHD (developed by Microsoft). To import your existing virtual hard disk use Virtual Machine Manager under File menu of VirtualBox. Then click Add and browse for the correct file. Starting now the hard disk is prepared to be used in virtual machines from you VirtualBox profile. Creating new machine is very easy, just follow instructions in the New Virtual Machine Wizard.
During playing with virtual machines with Windows operating systems you could face a problem when first login into the system. Windows has a activation mechanism which depends on the actual hardware – meaning reactivation is necessary. You are not able to take you disk and place it to another computer. Sometimes you could even face problem running some programs or the whole system because previous drivers does not work in the new environment.
When important hardware is changed, Windows gives you 3 days of normal use to let you finish reactivation. But there is a problem when you have VMware Tools installed on the guest operating system. In this case you will see message similar to this: This copy of Windows must be activated with Microsoft before you can log on. If you click Yes and try to activate Windows over internet, you’ll find out that there is no internet connection available. I have spent a lot of time trying to remove drivers or VMware Tools using Safe Mode, but I was unsuccessful.
The simplest solution is to open the machine using VMware (for the last time 
) and uninstall VMware Tools from the guest OS. After that you are able to run the system under VirtualBox software and install necessary drivers to be able to reactivate windows over internet.
Of course you can use the other two methods to activate Windows, but that is not comfortable for me.
If you have time playing with VirtualBox machine settings and PC configuration, you can try to migrate machine without reactivation of Windows. For more information look at the article on page http://www.virtualbox.org/wiki/Migrate_Windows.