If you are using GRUB:
- go to the /etc/grub.conf file
- there should be a line like default = ?
- change that to your RH7.2 partition #
See an example from the LQ archive here:
http://www.linuxquestions.org/questi...003/02/1/44091
If you are using LILO, you will have to change your /etc/lilo.conf file.