Well, VirtualBox is in the MINT repos and you can just install it using the software manager.
There is also this how-to site if you need USB support: http://www.khattam.info/howto-instal...010-11-20.html
Creating a virtual drive and machine and installing Windows there is the subject of several how-to documents: I recommend you google for it or check the VirtualBox forums. (Easier with an ISO image of Win7, but you can attach the cdrom drive to the virtual if you have media.)
If you select the dual boot option, you will want to either:
1. WINDOWS first
a. install Win7, leaving adequate space not partitioned to have room for mint
b. install mint in the free space
2. Linux First
a. install mint, leaving space for Windows
b. Install Win7
c. discover that the MS install has overwritten your MBR and you must use the Mint media to re-install grub to your MBR
d. let grub detect bootable images and rebuilt your boot configuration.
e. sigh in relief when you reboot and get a menu with mint AND win7.
f. enjoy (finally)
Whatever you choose, feel free to ask about more detail or references for the option you select.
Whatever you do, do not expect Microsoft to assist. This is not exactly their preferred scenario!