You're running a 64bit system. You have to modify another file in C:\Windows\SysWOW64\es-ES
Most, but not all, system files are doubled up in the 64 bit system. Always do a search first.
And don't think it is good enough to modify, say, just the sytem32 file and replace the two system files with just that one. Most of the time they are slightly different. You have to modify both. The only exception I've found to this (so far) is imageres.dll.