Changing language and localization

Hello.
I'm living in Spain for some time now but I speak English; I do speak Spanish too but I like to have the software in English. So, as I bought Windows here, it is in Spanish and I wish to change it to English. I already set location and format to English, but it still shows everything in Spanish.
Another thing that really bothers me is that if I download i.e. drivers for my VGA and even I specifically chose English, upon installing, it changes to Spanish. The same goes for most games that I guess read somewhere in Windows that I'm in Spain or something so they automatically install in Spanish.
So, first, how can I change the language in Windows? I don't have any option like "show text in English" in the Language Configuration settings.
Second, what do I have to change so installers pick English as install configuration?
Thanks for any help.

Are you familiar with loading registry hives remotely? If you are , I can talk you through it.

I assume you bought the machine with Home Premium preinstalled?

Before trying anything, make a backup image of your windows 7 partition and store it somewhere safe ( preferably an external HD ).

Macrium (free) will do image backup job nicely and will only take a few minutes.

Macrium Reflect FREE Edition - Information and download

In Macrium main window , click "Other tasks" > create recovery disc>tick the Linux Option and burn it to a cd.

You will need that to restore the image.

I bought the parts for a new PC because the old one was dying, so I bought Home Premium too. The thing is that as I bought the parts, I got the PC assembled by the tech support, which included installing Windows, I guess if it had the option to chose language, they chose Spanish. I already installed games and software, I really would like to skip another installation.