Most Windows computers do not have the option to change language. What version of Windows do you have?
Perhaps your only option is to do a fresh install of Windows.
You will need to buy a new retail version of Windows. Only Windows 7 and 8 are currently offered for sale. But, they might not run well on an older laptop.
Perhaps you can find some friend to help you install a copy of Linux. You can get a free copy of Ubuntu Linux that should run on your older laptop.