If you have Windows 8, you can easily switch back and forth between the English and Spanish keyboard. If you have Windows 8, send me a message on here, and I´ll tell you how to configure Windows 8 for it. =)

You can use this online Spanish keyboard: http://www.lexilogos.com/keyboard/spanish.htm

You can type á, é, ó, í, ú by pressing ' once and then the vovel. I don't think there's any way to type ñ unless you download the Spanish keyboard.

I have used http://spanish.typeit.org/ on several occasions. Not as convenient as having the Spanish keyboard, but it works for most situations.