Like this, i found error when installing Centos from media fdisk and the i search from internet Just share for my experience. If your finish installing centos when you try boot from HDD and then look error GRUB but if you booting from fdisk your system running well please follow this step :
1. Please booting your system from fdisk again<
2. Login with your user
3. Install GRUB For make sure your GRUB system on the disk
# grub-install /dev/sda
4. Configure your boot-loader first boot from hdd0, change file:
default=0 timeout=5 splashimage=(hd1,0)/grub/splash.xpm.gz hiddenmenu title CentOS (2.6.18-308.el5) root (hd1,0) kernel /vmlinuz-2.6.18-308.el5 ro root=/dev/VolGroup00/LogVol00 initrd /initrd-2.6.18-308.el5.img title Other rootnoverify (hd0,0) chainloader +1
Good luck and if your system always error don’t won’t give for trying other solution don’t reinstall your system, this is finally decision.