Disc image errors

Can anyone help me, I have just done an entire drive image of my machine which is partitioned, prior to installing Windows 7, to a external Drive It did complete but at about 79% I had a error message, "unable to read disk Sector" then listed several ten digit numbers, after I clicked to ignore, it completed. My Computer now shows data on the external drive in two partitionsas it should but the the progress bar on the main C: partition is shown in red. where all other drives are in green. My question is is this ok or does it mean that the main C: partition has not completed correctly. Many thanks for any help given. Regards J Baker