getting back dual boot ability

http://www.centos.org/docs/5/html/5.1/Installation_Guide/s2-rescuemode-boot-reinstall-bootloader.html
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Installation_Guide/ap-rescuemode.html#s2-rescuemode-boot-reinstall-bootloader
http://linuxhelp.blogspot.com/2005/11/how-to-repair-corrupt-mbr-and-boot.html