You can't actually run Linux inside Windows with VirtualBox or VMWare. It
is like a separate computer that you have access to without leaving
Windows, but you cannot run Linux applications without the virtual machine
running. They are two separate machines that both share your processor,
RAM, graphics card and devices. It runs in a window inside Windows.

To actually run Linux inside Windows you need something like andLinux or
coLinux (Cooperative Linux) or TopologiLinux. In this case Linux
applications run inside of Windows with both Windows and Linux kernel
running simultaneously.

http://en.wikipedia.org/wiki/AndLinux
http://en.wikipedia.org/wiki/CoLinux
http://en.wikipedia.org/wiki/TopologiLinux

There is also Ulteo which is more cloud based and commercial, but it is
impressive.

http://en.wikipedia.org/wiki/Ulteo


There is a way to *install* Linux in Windows as well called WUBI, but you
need to re-boot to *use* Ubuntu. It is the same as dual booting in many
ways, but you do not partition. Ubuntu runs from the C: drive and when it
reboots the Ubuntu installation is mounted like a hard drive.

Virtual machines are good for people with fast computers and processors.
They are full installations and once you learn how to share devices and use
them to move files back and forth then it is a good set-up. It is bass
ackwards though to run Ubuntu in Windows. It is better to run Windows in
Ubuntu because the host (Windows) should be the more secure platform and
Linux is way more secure and stable than Windows. You can do it but you
lose the advantages of Ubuntu.

The coLinux options are more limited. It is something like the Wine
experience in Linux. WUBI is a step that could precede a full
Linux installation on its own partition. All of these ways have advantages
and disadvantages.

Let us know what you are trying to do and we can help. There is no trick to
any of them.