Hello there!
Perhaps it is too late for this warning: The instructions given only apply for the 32 bit version of OpenFOAM 1.3, if you try to follow them exactly for the 64 bit compilation you will run into troubles, I do not have a 64 bit machine to test this, so I don't know what could happen. Please see advice by MKW87 above (thanks for this!) and read the release notes included in the OpenFOAM distribution regarding the installation on 64 bit environments...

Cheers