[ubuntu] I can't boot my Windows 7 after update Ubuntu

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http://ubuntuforums.org – I installed both windows 7 and Ubuntu on my disk, now I can't boot windows 7. I think it's something wrong with greb or hard drive sequence? chainloader +1 returns invalid signature. I thought it's the reason cause the problem. following information I think might helpful, if you need anything else, let me know. xinerd@xinerd-ThinkPad-Linux:~$ sudo fdisk -l [sudo] password for xinerd: Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 (Hardware)