64 bit guest on VirtualBox

Hi, I have the SUN VirtualBox 3.1.0 for x86_64 installed on my openSuSE PC, but how do I do to install a x86_64 system on it???

The same way you install any OS. With the Install media, which will need to ne _64 in this case.

Same as any other guest OS. But 64-bit guests will only work if your hardware supports something called VT-X/AMD-V.