1- Setup a virtual HD and install windows on it.
2- From VBox settings, go to 'shared folder' and add new folder. also you may check automount option.
3- Download virtualbox additions CD , and it should be same as your VBox version (ex: VBoxGuestAdditions_4.2.4.iso)
4- Add the iso image to your virtual devices and boot into windows
5- From windows open CD and install the additions, this will install many drivers and you may need to reboot windows.
6- From windows go to 'my computer', you will find your shared drives. enjoy!
