Let me try my best to answer your questions. For starters, you can obtain a distribution from the the official websites of the distributions or from www.linuxiso.org
. There are alot of places where you can obtain them. I don't know where you live so just choose a mirror that's closest to you. The main thign that Microsoft has but GNU/Linux doesn't is software compatibility. If you use GNU/Linux, you must be prepared that almost all of the software you own now will not run on GNU/Linux. However, there are many excellent alternatives. You might want to check this out. http://www.linux.ie/newusers/alternatives.php
Linux is FREE as in free speech, not free beer. For more on this you might want o check out http://www.gnu.org/philosophy/free-sw.html
. Of course most distributions are free as in no-cost but there are a few like Suse that charge. You can partition and do system tasks like in Windows and maybe even in greater detail as GNU/Linux is extremely customizable and modifiable.
Microsoft Word will NOT run on GNU/Linux. All .EXE files do not run on GNU/Linux. However, there is a sort of " Windows emulator" called WINE that allows you to run Windows software on GNU/Linux by simulating a Windows environment. Its still experimental so some software will run and others won't. Personally, I've had great success with it. I've managed to get Microsft Office, Star Wars Jedi Academy, GTA Vice City, Call of Duty and many other Windows software working under WINE. Details at www.winehq.org
DirectX isn't available on GNU/Linux but the alternative is OpenGL. The security features in GNU/Linux are far more advanced than what is available on Windows so your com will be much more secure. Not to mention that all 55,000+ viruses and malware will not run on GNU/Linux. So GNU/Linux users are pretty safe.
Hope I've answered your queries well enough. Pls post any more questions you have here.