I have ELF binaries complied with a previous version, and they work with RedHat 6.2. However when running them under RedHat 7.0, the file exists, but does not run, and claims 'File does not exist'.
This means they are libc5 binaries. Red Hat 7 does not support those anymore; however, you can install the "compat" rpms from version 6.2 though. Iirc the packages are ld.so-1.9.5-13.i386.rpm libc-5.3.12-31.i386.rpm and perhaps (I'm not sure, try without it first) compat-glibc-5.2-2.0.7.2.i386.rpm you can get them from http://www.mirror.ac.uk/sites/ftp.redhat.com/pub/redhat/redhat-6.2/i386/RedHat/RPMS/%5Bpage=3%5D