I got this error on my screen when booting:

kmod: failed to exec /sbin/modprobe -s -k block-major-8, errno = 2
VFS: cannot open root device "sda2" or 08:02
Please append a correct "root=" boot option
Kernel panic: VFS: Unable to mount root fs on 08:02




Grub.conf:
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this 
file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/sda2
#          initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=10
splashimage=(hd0,0)/grub/splash.xpm.gz
title CentOS-3 (2.4.21-32.EL-new)
        root (hd0,0)
        kernel /vmlinuz-2.4.21-32.ELnew ro root=/dev/sda2 hdb=ide-scsi
 
title CentOS-3 (2.4.21-32.EL)
        root (hd0,0)
        kernel /vmlinuz-2.4.21-32.EL ro root=LABEL=/ hdb=ide-scsi
        initrd /initrd-2.4.21-32.EL.img
title secondboot
        rootnoverify (hd0,0)




[root@localhost grub]# df -ka
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda2             76769884   1835016  71035092   3% /
none                         0         0         0   -  /proc
none                         0         0         0   -  /dev/pts
usbdevfs                     0         0         0   -  /proc/bus/usb
/dev/sda1               147766     11070    129067   8% /boot
/dev/sdb2             73901376     32828  70114560   1% /data2
/dev/sdc1             76920416     32828  72980180   1% /data3
none                    507948         0    507948   0% /dev/shm
[root@localhost grub]#