Possible Duplicate:
Grub rescue - error: unknown filesystem
I installed Ubuntu 11.10 alongside Windows 7. When I restarted my pc it showed unknown file system and grub> . I googled it and found something after which it is showing only grub> Now I'm using a live cd and trying to find any other solutions. All the files in partition where Windows 7 and Ubuntu 11.10 are installed, are present. Also, I'm posting the output of fdisk -l, I hope that will help.
ubuntu@ubuntu:~$ sudo fdisk -l
Disk /dev/sda: 500.1 GB, 500107862016 bytes
224 heads, 19 sectors/track, 229504 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0bc187fb
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 206847 102400 7 HPFS/NTFS/exFAT
/dev/sda2 206848 102399999 51096576 7 HPFS/NTFS/exFAT
/dev/sda3 102400000 307199999 102400000 7 HPFS/NTFS/exFAT
/dev/sda4 307202046 976771071 334784513 f W95 Ext'd (LBA)
/dev/sda5 307202048 512002047 102400000 7 HPFS/NTFS/exFAT
/dev/sda6 664348672 675837951 5744640 82 Linux swap / Solaris
/dev/sda7 675846144 839686143 81920000 7 HPFS/NTFS/exFAT
/dev/sda8 839688192 976771071 68541440 7 HPFS/NTFS/exFAT
/dev/sda9 512004096 660273151 74134528 83 Linux
/dev/sda10 660275200 664336383 2030592 82 Linux swap / Solaris
Partition table entries are not in disk order
Disk /dev/sdb: 4002 MB, 4002910208 bytes
32 heads, 63 sectors/track, 3878 cylinders, total 7818184 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x01443411
Device Boot Start End Blocks Id System
/dev/sdb1 * 63 7818047 3908992+ b W95 FAT32
ubuntu@ubuntu:~$
Any help would be greatly appreciated.