Installing mcrypt

I am installing mcrypt on a linux server. I first installed libmcrypt 2.5.7 and now am working on mcrypt 2.6.4. When I do a ./configure for mcrypt 2.6.4, it gives me this error: checking for libmcrypt - version >= 2.5.0... *** 'libmcrypt-config --version' returned 2.5.7, but LIBMCRYPT (2.5.6) *** was found! If libmcrypt-config was correct, then it is best *** to remove the old version of LIBMCRYPT. You may also be able to fix the error *** by modifying your LD_LIBRARY_PATH enviroment variable, or by editing *** /etc/ld.so.conf. Make sure you have run ldconfig if that is *** required on your system. *** If libmcrypt-config was wrong, set the environment variable LIBMCRYPT_CONFIG *** to point to the correct copy of libmcrypt-config, and remove the file config.cache *** before re-running configure configure: error: *** libmcrypt was not found There has only been one version of libmcrypt (new server), so I'm not sure why it thinks there is a 2.5.6 version on it. Where do I find the LD_LIBRARY_PATH enviroment variable to change it? Or is there another solution? Thanks! -Mike