Your whole computer reverted languages?
Well, at the bottom right corner, where the task bar is, you should see small, white, 2 letter word.
Not really a word, but this indicates which languages your keyboard is in.
I'm assuming it is set to English, since you can type just fine.
Next, your whole computer.
1. Start
2. Control panel
3. Language and regional options
4. Advanced
5. should be the first option there, change it back to English (where ever you live)
If that's not the problem, please explain better.