The cmder program is an open-source software that you can download as either a mini version of only 6 MB, or as a complete professional version with more than 40 MB. It's a console emulator that you can also easily transfer to a USB flash drive, so it's highly portable. However, there are quite a few other free emulators for Windows available, but this program has been designed from frustration to frustration, as many users reported problems with compatibility and smoothness. Fortunately, I found a program that works well with my laptop.
I use cmder because it allows me to play old PC games on my new laptop, without having to use the game CD anymore. A lot of people don't realize it, but you can actually load up your Windows PC using a "rom" - that's a memory stick that allows you to load up a particular software package. This software package will load up your computer with whatever programs it needs to play your game, and the command prompt comes in handy if you need to access files on your hard drive.
You can either load up the cmder application, then open Microsoft Visual Studio (the free visual studio) console, type "help" into the text box, and then follow the instructions it gives you. If you get confused by the cmder installation wizard, here's a quick recap: just follow the instructions on the screen, and then follow them again as described in the cmder read me file. I was able to load up the cmder console pretty easily and got started with the visual studio install process.