Windows is by far the most used OS in the world. Windows comes with another OS within it, Dos. This is what Windows starts from, and is built as a parter to it. Windows was developed by the Microsoft corporation, and deserves a lot of credit. There are two main versions of Windows out: Windows NT and Windows 2000. Windows 2000 is mostly used for your average PC user. NT is used by businesses and was built for that type of usage, and it's great for hosting Web sites.

To really get to know Windows, you have to look inside the your OS, learn what each script within it is doing, why it is doing it, and how to edit those scripts. Most people never take the time to do such things, even some sysadmins. Those people are the ones who will be least likely to find out you've been inside their computer. To start off, here's a list of the most important files in Windows, not in any specific order, and a brief description why they are important.

1. explorer.exe - the main program Windows runs on.
2. run.dll - the most important .dll file on Windows.