After some checking I found out that my OS was a 64 bit OS and everything should work as far as I could see. However, only 32 bits options where available. As it turns out Windows 7 in combination with virtualbox is not allowing you to run 64 bit guests when certain virtualization is not enabled in the bios of your machine.
After turning on "Intel Virtualization Technology" and "Intel VT-d feature" virtualbox again allowed for running 64 bit guests.
Just a small reminder for everyone who runs into this issue. In case you have this enabled and it is not working, make sure that you disable Hyper-V on windows.
For more background information on this you can refer to ticket 12350 on the virtualbox website.