I have been dual booting a computer with Ubuntu 8.04 and xp pro for about as long as 8.04 was out. I recently upgraded to 8.10. Until now I haven't had problems but now I'm getting error 21 and windows won't boot from grub saying the selected drive doesn't exist. I count from 0 to the windows grub line and that is correct. I have as Asrock 775 800 mobo. With this BIOS I have a boot menu feature. Selecting the hard drive for windows it boots right up. Using the grub menu 8.10 boot right up. I did recently have to change the line number after an update because it began booting into memtest. When attempting to boot windows from the super grub disk i get this

map (hd0) (hd1)
map (hd1) )hd0)
rootnoverfy (hd1)
chainloader+1
boot
grub loading stage 1.5

I just backed up and reinstalled windows after a Dban. What can I do here?

Best starting point would be to post the output of 'fdisk -l' and the menu.lst file in /boot/grub directory (need to do as sudo). How many drives, 2? xp and Ubuntu on separate drives? Did you do the xp backup/re-install before or after you started having this problem? I assume you are planning to boot both systems with Grub?

Thanks yancek. I was able to correct it. Part of the problem was me. the BIOS I have is a little unfamiliar to me and it took a while to figure it out. The hdd with windows wasn't recognized in BIOS as it was third on the hdd boot device list and so not in the first two. I changed the order but don't know how it got that way in the first place. It works well now.