How can I change the spell check and auto-correction language of IE10/Windows8?

Check the Control Panel. Which languages do you have installed? If you have only Norwegian, try adding English as well:

You can then switch languages from the language icon in the taskbar.

You can also press ⊞ Win+C to bring up the Charms bar, select Settings / Change PC settings / General and modify the Spelling and Language options as required:

BTW, here's a complete list of supported spellchecking dictionaries and language/locales in IE 10.

Update: How do you type and spell-check in one language, but use the keyboard layout of another?

The problem with switching the input language is that normally the keyboard layout also changes, which is irritating. Here's what you can do. Say you have a German keyboard layout but normally type in English (input language), and want English spell-check (proofing language) as well.

Add English to the language list and make it your primary language by moving it to the top. Now click the Options link:

Here under Input method you can Add an input method:

So now you can have English as the input/proofing language but German as the input method/keyboard layout. You can subsequently press ⊞ Win+Space to switch between available combinations:

The answer above is missing the most important part: how do you SWITCH languages in IE. After you have installed multiple languages, when you want to switch languages you use either the language bar or the language icon in the taskbar, right by the clock. You just click it and select the right language. All you type after that will be spell checked in the new language.

I just tried typing in English on the Sami Extended Norway (ÁŠERTŦ) input and couldn't type the word "want" because I could not find a W!

Then, with my language set to English, I added the Norwegian QWERTY keyboard. Leaving my display language as English, I was able to type in English on the Norwegian QWERTY keyboard using the on-screen keyboard on my touch screen, and the spell-checker did its job correctly after I typed "bearsss" instead of "bears". So, if you have a Norwegian QWERTY keyboard, try the steps in my original answer to see if they help.

All of the keyboard languages are under input method in Windows 8. You change the keyboard language by changing the input method. Just as an example, for my regular imput method, I use the QWERTY keyboard. I use it in English. By following the steps I provided above, I add a QWERTY keyboard in Spanish, and then I am able to type ñ, ¿, and other characters that are not available in English. In Windows 8, Norwegian and Norewegian with Sami are available in QWERTY. Sami Extended Norway is available in ÁŠERTŦ.

If this is solution does not apply to your problem, I hope that at least it will help someone else.

Write something somewhere then right click on the word then spell-check options and choose the language you want if you have more than 1 on the list that opens. If not add more in the control panel. :)