I installed Ubuntu yesterday via a bootable USB drive, created with unetbootin. Everything went very well, but now the computer does not boot unless the USB drive is plugged in. If it's not, then when the computer boots, the boot sequence screen just appears and if I select the hard drive, it will just reboot and go back to this boot sequence screen, until I plug in the USB drive.

Any ideas? Thanks a lot for your help!

UPDATE: Having some valuable data on the machine, I would prefer a solution that doesn't involve reinstalling, but from the first replies, I guess this may be what I have to do eventually. Thanks!

GM

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EDIT: output of sudo fdisk -l below

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: 0x000742dc



   Device Boot      Start         End      Blocks   Id  System

/dev/sda1            2048  1449474047   724736000   83  Linux

/dev/sda2      1449476094  1465147391     7835649    5  Extended

Partition 2 does not start on physical sector boundary.

/dev/sda5      1449476096  1465147391     7835648   82  Linux swap / Solaris



Disk /dev/sdb: 4009 MB, 4009754624 bytes

255 heads, 63 sectors/track, 487 cylinders, total 7831552 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: 0xc3072e18



   Device Boot      Start         End      Blocks   Id  System

        /dev/sdb1   *        8064     7831551     3911744    b  W95 FAT32

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EDIT2 bootinfo output:
http://paste.ubuntu.com/1006423