IMPORTANT NOTE: The instructions given here assume that you have exactly one Windows virtual machine (vm), and that this one vm will be backed up to the directory ~/Windows_Backup/ in your Linux home area. Some users have multiple Windows vm's. If you are one of these users, and you wish to back up more than one virtual machine, create a separate directory under ~/Windows_Backup/ to house the backups from each of your different virtual machines. Ex: ~/Windows_Backup/WinXP/, ~/Windows_Backup/Win7, ~/Windows_Backup/Win7-OLD, etc. This way the backups of your different virtual machines are kept separate and nothing is accidentally deleted or overwritten.
On Linux, open a terminal and type the following commands:
Type: mkdir ~/Documents/Windows_Backup
This will create the directory in which your Windows backups will be placed
Type: chmod 0700 ~/Documents/Windows_Backup
This will secure the directory by setting permissions such that only you may enter the directory or see it's contents
In your Windows VirtualBox:
Open the Cobain Backup control panel by clicking on the icon in the system tray.

Click on
Create a New Task

Under
General:

Task name: Backup
Uncheck: Create separated backups using timestamps
Check: Use Volume Shadow Copy
Backup type: Incremental
Under Files:
Under
Source, click:
Add, then
Directory in the pop-up menu that appears

Select your user directory

(In this example, the user directory is named “
User”, your actual user directory may be named differently.)
Under
Destination, click
Add, then
Manually in the pop-up menu that appears

Click: OK
Under Schedule:
Select how often you would like Cobain Backup to back up your files, and click
OK

(The default is once daily. This is the suggested schedule, unless you have a legitimate reason to change this setting.)
-
Click: OK
Check your work:
In your virtual machine:
Open the Cobain Backup control panel, select
Backup from the task list, and click
Run the Selected Tasks

Click:
OK

You will see Cobain Backup do it's thing, and log it's activities

From Linux:
Open a Nautilus file window and navigate to your
~/Windows_Backup dirctory

You should see all of your files here