Display Language - Windows 7 Professional

I just purchased a Dell Vostro in Costa Rica and did the initial set-up of Windows 7 Professional in Spanish (when first starting up the computer). I now want to change the display language (for all menus,internet explorer, startup menus, help, trash etc) from Spanish to English and cant seem to make it work. When I go into the regional language options, it shows that I have selected everything in English, format, region setting in USA, etc but the systems remains with everything in Spanish. I have tried about everything I can find and have not been ale to do anything about it. Additionally, even though I have a registered Dell account, have registered the computer in the US, etc I cant even do the Windows Anytime Upgrade to Windows to allow me to install language packs (if this is what I need to change the language). Any suggestions?

Thanks all