Before you start doing some of the drill exercises I recommend you changing your keyboard setting to US International. Here is how:

In Windows 2000 Click Start (lower left corner)

Click Settings
Click Control Panel
Double Click Keyboard
Now you see your keyboard setting, probably [En]glish United States 101, but what you need is United States International
Click Properties
Click to Pull down menue
Choose United States - International
Click OK
Now, the computer probably asks you to insert your Windows installation disc
Insert it and press OK
Windows now installs the new keyboard setting and probably tells you to restart your computer

In Windows XP

Click "Start" (lower left corner)
Click "Control Panel "
Double Click "Regional and Language Options"
Click "Languages"
Click "Details"
(Under Default input language you will probably see "English (United States)"
Click "Add"
Mark the little check box "Keyboard layout/ IME
Now look for "United States-International" and click OK
(this brings you back to the screen "Text Services and Input Languages")
Under "Installed services" you should see "English (United States)" and "United States-International"
Under "Default input language" choose "United States-International"
Click "Apply
Click OK
If the computer asks you to insert your Windows installation disc, insert it and press OK
Windows now installs the new keyboard setting and probably tells you to restart your computer

That's it. At the buttom of your screen, on the right side, you will see a little keyboard sign, which can be used to switch between the "English (United States)" and "United States-International" keyboard setting

When you hit the single quote key in the "United States-International" keyboard setting and then a, e, i, o, u now, you will see á, é, í, ó, ú on the screen
For ñ, you hit Shift  ~ and n