Earlier today I installed Windows 2008R2 SP1 evaluation on VirtualBox on my Windows 7 x64 PC. As of this writing I have virtualbox 4.1.6 installed on my machine.
Obviously the first step is to download the Windows 2008R2 SP1 iso file. The next step is to enable the Virtualization Technology for your PC. Without Virtualization enabled, You’ll most like get an error. Something like this ERROR: VT-X is not available or enabled.
You can enable this feature (if available and supported on your PC) through your BIOS setup. Here is a screen of the BIOS setup on my PC:
I enabled: (1) Virtualization Technology (2) Virtualization Technology for Directed I/O
Here is a summary of the settings on VirtualBox:
From here on Windows 2008R2 SP1 should install itself. Below are a few screen shots: