I restored a tar backup of a Centos3 x86_64 box using a Centos4 x86 machine to format the disk and untar the files. Then I used the install cd to install grub on the actual machine but when it booted it said the filesystem had errors and fsck refused to fix them because the filesystem had newer features. Is there a way to make a backwards-compatible filesystem in the newer version and is the difference documented somewhere?