The recent edition of Redhat5.3 64 bit edition is available in Torrent site freely which is having the original key and free online support.
Five major features of RHEL 5.3
1. ext4 file system support
2. 730 bugs fixed after RHEL 5
3. ALSA Support for new hardware also
4. Included enhanced lot of server RPMS.
5. Latest Kernel kernel-2.6.18-128.el5.src.rpm
There are plenty of special features included in RHEL5.3. The link following leads to go over there.
Refer the following link for download it