Vector masks have two major advantages:
1) You can edit them after you've drawn them.
2) You don't lose the rest of the image.

You'll see what I mean, let's go on.

You'll be using the pen tool to draw your mask, and the white arrow to clean it up once it's drawn.

Before you begin, make sure your image is on it's own layer, and there is a blank white layer behind it.

Select the pen tool, zoom WAY in, and start clicking along the outside of your object. This is just like using the polygonal lasso tool.

I reccommend that you stay just inside the edge. Your selection will look cleaner this way.

If you feel comfortable with it, you can use the lines of influence to draw your curves. Do this by clicking and draging when you make your points.

This method is faster and more accurate, but takes a little practice. If you want to be a grand master, you ought to learn it.

Going on, once you've made it all the way around your object, it should look something like this.

Now your image should look something like this! If parts of your mask don't look right, go back in with the white arrow tool and adjust your points.

Here I added a nifty background, a glow effect to the computer, and some pricing information. Looks like a pretty good deal doesn't it?