The Windows UI language? That usually requires an Enterprise or Ultimate edition of Windows to change it separately, otherwise you'd have to buy (or persuade the laptop maker to send you) an English copy of Windows.
As stated above you can only do this with ultimate version of windows 7 if that's what you have but respectively you can download language pack from some website or your other choice would be to do this: install ultimate, put language pack and then use HOME PREMIUM SERIAL KEY...if you have ultimate installed and validated just write in CMD