Portable Ubuntu is a Linux distribution, variation of Ubuntu, which will allow you to run Linux within Windows as if it were a program or process. So those who wish may prove what is seen as the free operating system, without the complications of configuring a virtual machine or emulation.
You need only download the installation of Ubuntu Mobile, which holds about 440 MB and when uncompressed requires 1.86 GB of space. Then, just double click the file run_portable_ubuntu.bat, which will be in the root directory in the folder where you unzipped Portable Ubuntu, you can start the distribution.
That is nearly complete, with the menu of Ubuntu and all its component applications, which can add many more just go to Synaptic Package Manager. What is surprising is that its creator says not to use more than 50MB of RAM for Ubuntu Mobile as a process, a truly negligible amount by the standards of today, and especially if we think we are running Ubuntu within Windows.
For those who want to try Linux without changing anything about your system (even the boot order is essential to be able to try a Live CD),Ubuntu Mobile is no doubt the best option, since it does not require any configuration.