hard drive - VirtualBox: Windows 7 says it's not genuine

I've set up a Windows 7 guest machine under Windows 7 using oracle virtualbox 4.2. This Windows Guest has its own product key which corresponds to the boxed set I purchased for the sole purpose of running it in virtualbox. A few months ago I backed up my Windows 7 virtual box virtual disk image on an external hard drive. Now that the Windows 7 started to malfunction, I deleted it, and copied it back from my external hard drive.

However now it's telling me that the version of windows is not genuine. How can it be. There is nothing else using the same product key, unless someone hacked into my backup folders and stole the protuct key from there and used it on a machine of their own.

Thanks.

Answer

1. Click Start Button


2. Right-click Computer.


3. Select Properties.


4. At the bottom of the window, click Activate Windows now.
   

In the Product Activation Wizard, follow these steps:

1. Click Use the automated phone system to activate

2. Click the drop-down menu, select the location that is nearest to you, and then click Next.

3. The Product Activation Center telephone number is displayed under Step 1.

For more information about how to activate Windows 7, go to the following Windows Online website:
Activate Windows 7 on this computer

Source

Please Read:

Just an added note, sometimes the phone system will tell you that you have installed this key the maximum number of times. It will then ask you how many PCs are running that copy, and you can say "zero", which will allow you to proceed with activation.