after the instalation there was a GRUB prompt so i went into the rescue mode.

i did these steps...

To restore Grub
1) Boot from the first CD
2) Type: linux rescue
3) select: skip media test
4) select: of for language
5) select: ok for keyboard
6) select: continue with rescue
7) select: ok with rescue
8) type: chroot /mnt/sysimage
9) type: grub-install /dev/sda

command line grub-install /dev/sda (cause i have serial ata in raid 0).
After i restarted my computer and i got

"GRUB Loading stage1.5.

GRUB loading, please wait...

Error 2"

someone know why??

Post fdisk -l
and
/boot/grub/menu.lst or /boot/grub/grub.conf

fdisk -L

Disk /dev/sda:37.0GB, 37019566080 Bytes
255 heads, 63 sectors/track, 4500 cylinders
Units = cylinders of 16065 x 512 = 8225280 bytes

Device Boot Start End Blocks ID System
/dev/sda1 * 1 64 514048+ 83 Linux
/dev/sda2 65 4500 35632170 8e Linux LVM

Disk /dev/sdb:37.0GB, 37019566080 Bytes
255 heads, 63 sectors/track, 4500 cylinders
Units = cylinders of 16065 x 512 = 8225280 bytes


Device Boot Start End Blocks ID System
/dev/sdb1 * 1 4500 36146218+ 8e Linux LVM



GRUB.CONF

#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddemenu
password --md5 $1$lKLb0FXE$yKd6UDq42fLCXG7msqvcy
title Fedora Core (2.6.11-1.1369_FC4)
root (hd0,0)
kernel /vmlinuz-2.6.11-1.1369_FC4 ro root=/dev/VolGroup00/LogVol00 rhgb
initrd /initrd-2.6.11-1.1369_FC4.img

See if this helps;
http://www.linuxhomenetworking.com/linux-adv/raid.htm
I don't have a clue, but make sure your hardware is supported.

If the raid is "motherboard supported" it's probably a shonky software implementation rather than true hardware - despite manufacturers claims.
I'd be pretty surprised if grub worked in such an environment, although I haven't tested it.

My suggestion would be to have a small non-RAID /boot partition.

My motherboard is an msi k7n2 Ultra and i have 2 raptor 36Go 10 000rpm sata in raid 0