I've read the faqs and can find info on creating images but not of restoring them back to the hard drive.

I have created a dd image file of the complete hard drive /dev/hda on a removeable hard drive
using
dd if=/dev/hda of=/mnt/sdb1/image.dd

Now I am trying to restore the image back to the hard drive as an upgrade went wrong.
However
dd if=/mnt/sdb1/image.dd of=/dev/hda is not working.

I think I have to make hda writeable but I don't know the exact syntax of the command I need.
On the left of the desktop I can find icons for hda1, hda3 and hda7 which are currently on my machine but are currently unmounted.
What exactly do I do here?

Hope someone can help.

Regards
Brian C