It is important to backup your install of Windows 7 OS. Mainly because very few if any companies give you a Windows install disc with the purchase of your PC anymore. If your PC ever crashes in an unrecoverable way, you will not be able to restore your PC and have a useless POS. You would then need to request a reinstall disc or some other pain-in-the-rear process.

In Windows 7, it is really easy to avoid this situation. Click on the start button in your task bar. That's the little circle Windows logo thing(I'm not trying to insult your intelligence with my wording. I just have no idea of your Windows-fu level and want to be clear and concise). In the text bar type "backup."

Once the window opens, you will have to click on "setup backup" since, I assume, this is your first time doing it. Then it is pretty simple. Just pick your back up medium (use one of your external hard drives and if you want to be really redundant, which is always good when talking about data, do it again to a writable dvd/bluray). The onscreen instruction are pretty easy to follow from there.

Feel free to message me if you need anymore help with it. I can always get on Skype or some other instant messaging app and walk you through it too.

As for the MAC. You are on you own. I am sure with even rookie Google-fu you can find a how to on it.