I am using Windows 7, not Windows 8, but from what I understand they are very similar (except 7 does not support touch screen).
Having said that, the International keyboard is already built into the system, but just needs to be added to your list of keyboards. Once it is installed you should have a little keyboard icon (or at least I have one) on the screen that allows you to switch between the strictly US keyboard, and the US International keyboard.
The layout of the keyboard is very much the same, except that when you use the International keyboard you hit the apostrophe ' then the letter you wish like "e" and you get é (there, I just did it). Other than those few letters, the two keyboards are the same (I'm using the International keyboard right now). If I wish to make an apostrophe I have to hit it twice when I use the International keyboard, but switching back and forth is easy. ñ is made by using the 'tilde' and then the letter.
For me this is much easier than using the ALT codes, which I keep forgetting anyway! Really you don't notice any difference when using the International keyboard unless you wish to make an apostrophe or a tilde, and it only takes a mouse click to switch back and forth.
Other than that I can't think of any other ideas at the moment.