"Preview" on a Mac

I'd just add to that, that if you're going to reboot, you may as well hold down the mouse button or space bar to cause the disc to eject before the system boots. You could also just hold down the option key, and when the icons start appearing, press and hold the eject button on the keyboard for about a second.

Preview will actually show you the contents of many different file formats, including videos in many formats including "avi" and "flv" (Flash format), both Excel and Numbers spreadsheets, both Word and Pages documents, both PowerPoint and Keynote slide presentations, (though you can't play the slide show, you have to select each slide from the thumbnail images in the left column) and many more file formats.

As an aside, an interesting way to see slide show contents, although not very clearly, is in icon view, where if you hover the cursor over a slide show icon, left and right arrows will appear and you can scroll through the slides, though only at the icon's tiny size. Interesting that this can be done, in any case, and is quicker if you only want to see if the slide show is the one you are looking for. (See grammar note above.)

Preview is a really good way to view content that you may not even have an app that it can be opened with. Yes, grammar nazis, I know it should have been "with which it can be opened", but who cares?

This is also real handy when you have a window of files, in either icon or list view, and want to see what a particular file is. All you have to do is hit the space bar, and a preview window opens showing the file if it can.

If you want to view a number of files that reside in a folder, just open that folder, hit the space bar on the first file you want to check, and then the up and down arrows will change to preview to the previous or next file. Up for previous, down for next. The best thing about this? If they are a mixture of file formats, you can see them all without having to open a bunch of different apps

What happens if you encounter a folder in list view, and want to see what is inside? just hit the right arrow to reveal its contents, and you can merrily scroll down and see what is what. The left arrow when hovering over an open folder will close it up again. A very useful feature of OSX.

Technically what you're referring to is called quick view, preview is a specific app that has been a part of OS X for a very long time, maybe the very beginning. Quick View didn't come along until about 10.5. Quick view is like a stripped down version of Preview which only does the viewing bit. Preview has a few minor editing features, like annotating PDF documents. You also cannot print with quick view, or view more than one file at a time.

Not really sure where your post came from though, since the OP wasn't talking about what preview can do, they were complaining about how it was apparently preventing them from ejecting a disc.