Computer language settings
Please visit this link for language settings in your personal computer
Once you finish the change successfully as per the instructions mentioned in the above website, then please
1) restart the computer
2) you will find an icon on the 'task bar' at the bottom right corner
of the screen, near the time and sound icon.
3) click the icon and change the language
4) sometimes computer can act little weird and may fix any language automatically. This does not happen very often but If it happens then just click the same icon and fix the language that you want to use.
Please try this if it works. If not then pls ask the person to mention as specific as possible about the kind of problem s/he has been facing.