I am trying to dual boot Windows and Linux on a machine at work. While I haven't used windows in a while, It is a process that used to work most of the time. But I haven't been as lucky with this particular machine.This machine is running Windows 7 with Ubuntu 12.04. After the Ubuntu installation grub never appears and the machine boots to Windows 7. So far, I have tried manually booting Ubuntu from the usb stick and installing grub again without  success. To help see my configuration, here is a partition layout. Disk /dev/sdb: 931.5 GiB, 1000204886016 bytes, 1953525168 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 Disklabel type: dos Disk identifier: 0x862b0218 Device     Boot     Start        End    Sectors   Size Id Type /dev/sdb1  *         2048     206847     204800   100M  7 HPFS/NTFS/exFAT/dev/sdb2          206848  614399999  614193152 292.9G  7 HPFS/NTFS/exFAT/dev/sdb3       614402046 1953523711 1339121666 638.6G  5 Extended/dev/sdb5       614402048  814399487  199997440  95.4G 83 Linux/dev/sdb6       814401536 1953523711 1139122176 543.2G 83 LinuxAlso the bios is using legacy mode and secure-boot is disabled. Apart from that it looks like re-installing grub didn't work, because the first 512 bytes are different from my laptop which has grub installed on mbr.Any ideas?
Dual booting Ubuntu and windows 7
linux;dual boot;mbr