I have a Firefox add-on called easyaccent. It allows people using Windows with an English keyboard to easily enter accented characers in Firefox -- when composing emails, typing gchats, or pretty much anytime they enter text in Firefox. You enter an accent by typing CTRL-<accent> followed by the key. So to type é you would hold down the Control key and type' (apostrophe), and then type e. This is the way accents work in Microsoft Word, and on Macs, but unfortunately Windows is dumb. You can also use a non-English keyboard layout, but if you're like me, you're used to your punctuation characters being where they are, and you just want to enter accents easily. You could also use the International keyboard, but then every time you type an apostrophe, you have to hit an extra space to tell Windows you're not about to type an accent, which also seems silly to me.
Here is a list of the accents and how to type them.
My add-on is available at the Firefox add-on page.