"Hard disk '____.vdi' with UUID {___} cannot be directly attached to the virtual machine 'Windows7′ ('___.xml') because it has 1 differencing child hard disks."

I have no idea what 'caused this error and it took me a lot of searching to find a good solution to it. Since it took me so long to figure out I decided I would post the solution here for my own reference and hopefully to help anyone else that faces the same issue.

For me the fix was amazingly simple. All you have to do is create a new virtual machine from scratch and use the existing hard disk image for the broken virtual machine.

• Load the VirtualBox Manager
• Click "New"
• fill out all the basic info
• On the "Virtual Hard Disk" tab select "use existing hard disk"
• Browse for your existing hard disk
• Select your .vdi file and click continue
• Finish the remaining steps and start up your new Virtual Machine

If you have trouble finding your virtual machine just look at the path in the error message it will be something like:

Windows:  C:\Users\Lenny\.VirtualBox\Machines\Windows7\

Mac: /Users/Lenny/VirtualBox VMs/Windows7/

replace "Lenny" with your username and replace "Windows7″ with the name you chose for the virtual machine that stopped working. You should use the .vdi file in that folder DO NOT use the .vdi in the "snapshots" folder.

Once I did that I started up the new virtual machine and everything started up just fine. Also, once I started it up once and shut it back down it actually fixed the broken virtual machine. You can either use the new one you just created or just delete it and go back to using your newly fixed (previously broken) VirtualBox virtual machine.

Luckily, there is a very easy solution (and don't say VNC… it sucks). There is a very easy way to enable remote desktop on Windows 7 Home Premium. Simply follow the instructions below and you'll be running a Remote Desktop (RDP) host on Windows 7 Home in a matter of minutes.

The First thing you need to do is download the Concurrent RDP Windows 7 RTM Patcher. You can get it here or here (mirror). Please, be safe and scan this file for viruses after you download it. I scanned it when I used it and it came up clean, but I don't host this file / didn't create it and you can't be too careful.

Now that you have the patcher downloaded we can start the process of unlocking remote desktop on your Windows 7 Home Premium computer.

1. Unzip the file you downloaded.
2. Right-click on the install file and click Run as administrator. If you receive a UAC prompt click "yes"
3. After this the Windows 7 RTM patcher will be opened in a new command window. It will look like this.
   

   Windows 7 Remote Desktop Patcher

   At this prompt feel free to read the text then press any key to start the process

4. Next you will see the following screen. This is asking if you want to allow multiple sessions per user. In most cases you do. So my advise is answer yes. So, you want to type Y and hit enter.
   

   Windows 7 enable Remote Desktop

    

5. Then you will be presented another question (pictured below) this will allow you to use a blank password on RDP. Again, I advise answering yes. Even if you say yes you CAN still use a password if you want, but if you ever want to use a blank password you can't if you answer no. Leave your options open and type Y and hit enter.

   

6. Wait and wait.. for me this step took quite a while. The patcher will now do all the work the double check that the fix worked. For whatever reason it waited a long time to ensure the service was actually listening for Remote Desktop connections. Once it's complete your screen should look like this.
   

   Remote Desktop Enabled on Windows 7

   Press any key and you should be all set.

On my computer for some reason it failed to properly configure the firewall. If this happens to you just go to the Windows control panel and click on firewall. Then, add an incoming TCP exception on port 3389 and you should be good to go.

Thats it now you can enjoy using remote desktop (RDP) on Windows 7 Home Premium.