My sister had the same problem (with Dutch and US English) and she said she fixed it by doing the following.
1. Go to the Control Panel>>Regional and Language
Options>>Languages
2. Click on Details(under Text Services and Input Languages).
You should see something called "Installed Services" now. You can use the "Add" or the "Remove" button to add and remove languages/keyboards.
For pictures to go along with these instructions:
http://www.microsoft.com/globaldev/handson/user/xpintlsupp.mspx
By the way, an easy way to switch between two keyboard settings is by pressing either Alt-Shift or Ctrl-Shift (I've heard both options and as I'm not on XP myself, I can't test it).
[edited to fix typo]