Try going to the Contol Panel, and then going to Regional and Lanugage Options.
Then go to the language tab of this window and press details.
You can then change the language of the keyboard, and the input languages. They might require a restart to start going.
To store a new one to use again, so you can easily swap, go to Add, and change the languages here. It will then be added to the list, and you'll be able to change it more easily.
If you have Windows XP, and on the taskbar there is a small EN symbol on the right, you can click this to access the settings to change them which will enter this menu.
I hope this helps