go to: http://www.froggie.sk/en/7lp64sp1.html

Run CMD as administrator and type:
DISM /Online /Add-Package /PackagePath: (example: c:\langpack\en-us) This can take quite a while

Then type

bcdedit /set {current} locale en-us (or whatever language)

then

bcdboot %WinDir% /l en-us

Then in regedit
HKEY_LOCAL_MACHINESY/system/CurrentControlSet/Control/MUI/MUIUILanguages
delete whatever language you don't want



dism /online /add-package /packagepath:d:\langpacks\en-us\lp.cab
bcdedit /set {current} locale en-US
bcdboot %WinDir% /l en-US