Re: How to run Windows along with Ubuntu 12.04 LTS simultaneously
You can mount your Windows NTFS partition under Ubuntu and open your documents using for example LibreOffice or OpenOffice (similar to guess what?). If it's only access to Microsoft Office documents, this could solve 95% - 100%.
VirtualBox is quite easy to set up, but making it work with an existing installation of Windows is a pain in the you know what.
If you run Windows 8, you could run Ubuntu on Hyper-V (I guess?). This is what Microsoft wants you to do and the reason they now "support" Linux with drivers (that allow to run Linux on Windows/Hyper-V).
I did the opposite and more: run Windows on Linux / Xen hypervisor with Windows having direct access to a dedicated graphics card for bare-metal performance (this is called VGA passthrough). This will only work with specific hardware features (VT-d / IOMMU) and is rather challenging to set up, but it gives you Linux and Windows running on the same computer at the same time, both with excellent bare-metal like performance. Data sharing can be over a Samba share, and since both communicate via a virtual bridge, data transfer speed is a non-issue.
Regarding performance: Virtualbox seems to improve but is still behind Xen and kvm. If graphics performance of the guest OS is important, for example gaming on a Windows guest, you got only two choices: Xen or kvm with VGA passthrough as mentioned above.
If you're new to Linux, try Virtualbox and reinstall Windows in a virtual machine. Or vice versa, use Windows as host and install Linux in either Virtualbox or Hyper-V.
LM18.1 64bit (Ubuntu 16.04) with a Windows 10 Pro 64 bit kvm guest using VGA passthrough