http://youtu.be/SgOMg65ZOEo
Written Steps:

Step 1: Open the application.

Step 2: Click New.

Step 3: Decide the name of your virtual machine then ensure Microsoft Windows is selected for the type.

Step 4: Select Windows 7 or Windows 7 (64-bit) depending on your type of operating system.

Step 5: Click Next.

Step 6: Decide how much RAM you would like to give to this virtual machine. I suggest around 2048MB if that’s available.

Step 7: Click Next.

Step 8: Ensure create a Virtual hard drive now is selected then click create.

Step 9: Ensure VMDK (Virtual Machine Disk) is selected then click Next.

Step 10: Ensure Dynamically allocated is selected then click Next.

Step 11: Specify the size of the virtual hard drive. I reccomend around 100GB if that’s available. Then click Create.

Step 12: Next, launch the virtual machine by selecting it then clicking Start.

Step 13: Select the drive that contains the Operating System you will be installing then click Start.

Step 14: Configure the language and area settings to suit you then select Next.

Step 15: Select Install Now.

Step 16: Ensure the checkbox is ticked then click Next.

Step 17: Click the Custom (advanced) setting then select the Virtual Machine Disk that you created during Step 11.

Step 18: Select Next.

Wait for the installation process to finish.

Step 19: Choose a username for the virtual machine account then click Next.

Step 20: Choose a password for the virtual machine account then click Next.

Step 21: Type in your product key if you have one available, otherwise click Skip – you’ll be able to activate Windows later. Alternatively click Next.

Step 22: Select Use recommended settings.

Step 23: Configure the time zone, date and time then select Next.

Step 24: Click the network type which suits your position.

Congratulations! If you’ve followed these steps correctly then you will have been able to successfully create and set up a Windows 7 virtual machine using the VirtualBox software.
Thank you for watching and I hope you found this tutorial to be helpful.