I have a windows 7 home premium computer and a windows 8 laptop.
I am thinking of putting my laptop's hard drive into my windows 7 PC as well as leaving the win 7 hard drive in there, so I can have two OS on my PC.
Is this possible to do and would I be able to switch OS quickly, or would I have to change the BIOS every time?
You can set up a virtual machine, you just need to find some how to videos. With a virtual machine you will start in your primary OS and after the computer is running you start up your other OS. If you choose the other way you will need to change the boot order every time you log in but it is easy.