"client only works on x32 bits" what tha ...?

Well i got this problem:

I downloaded the full client after a random D/C in arena. I cant move my ranger but well who cares ._.

And now i got this error when i opened the installer:

"The version of this file is not compatible with the version of Windows that is running. Check the computer's system information to see if you need an x86 version (32 bit) or x64 (64 bit) program and then please contact with the administrator"

I got the error on spanish because its my native language.

Just what i do now? ._.