How do I know if I have a Windows Computer or a Macintosh?

Look at the screen when the computer is on. If it has an Apple symbol in the upper left-hand corner, it's a Mac. Click on the apple and then select "About this Mac" to find the Operating System number. If instead you have a "Start" button at the bottom left of your screen, it's a Windows machine. Clicking on that start menu will usually display the Operating System number along the left side of the menu that pops up.