我的电脑里有 Windows 7 和 Ubuntu 12.04，在尝试安装和卸载 SD 卡后，我的 Windows 7“隐藏了自己”，当我打开电脑时，我可以进入 Grub 并选择
Windows 7 (loader) (on /dev/sda1)
但是，它说
error: no such device: B6606771606736F1.
error: invalid signature.
我如何恢复我的 Windows 7？当我sudo fdisk -l这样做时，它显示
Disk /dev/sda: 750.2 GB, 750156374016 bytes
255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0xfeff8cfd
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 523655167 261826560 7 HPFS/NTFS/exFAT
/dev/sda2 523655168 1359239167 417792000 7 HPFS/NTFS/exFAT
/dev/sda3 1359241214 1465147391 52953089 5 Extended
Partition 3 does not start on physical sector boundary.
/dev/sda5 1359241216 1448818687 44788736 83 Linux
/dev/sda6 1448820736 1465147391 8163328 82 Linux swap / Solaris
Disk /dev/sdb: 24.0 GB, 24015495168 bytes
255 heads, 63 sectors/track, 2919 cylinders, total 46905264 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: 0x74f02dea
Device Boot Start End Blocks Id System
/dev/sdb1 * 2048 46901247 23449600 7 HPFS/NTFS/exFAT
请帮助...