You can use the dual boot approach by creating a new partition and running your Windows 8 installation from boot-up. Note that if it's an upgrade disc, then you won't be able to do this.
Thanks for your input. That is what I am worried about. It is probably an upgrade version. I asked Microsoft via live chat and the person told me that Windows 8 that I upgrade will have a different license... So I don't know if my Win7 licience will just deactivate itself or something? Because if they are two separate licensees, then I could probably do dual boot though?