virtualbox.org

I am getting into Linux, spec. Ubuntu. I think I am going to start to use it as my main OS, but during the transition period, I want to still access my existing windows setup. Is it pos to copy all data from an existing windows setup and transfer it too a Virtual machine?

Sure is.
You can find how others are doing it by putting the following in Google.com:
p2v site:forums.virtualbox.org