Hello Papagei and welcome to Seven Forums.
I'm guessing you used the native Windows 7 imaging tool to create your system image. Couple of thoughts come to mind. Did you create/save the system image using disks or an external USB hard drive? The worst case scenario is the system image was corrupted or did not get created properly. If that's the situation it's unlikely that you'll be able to use that system image. Perhaps some other more knowledgeable Forum member will jump in with ideas on how to get the image to work.
Is the replacement hard drive the same size (or larger) as the original hard drive? If smaller the image won't work. It's also possible that the replacement hard drive is defective in some way.
Did you replace the original hard drive because it was failing? Or just to move to a larger hard drive? Or perhaps upgrade to a SSD? If the original hard drive is still working you may want to reinstall it and use a different imaging program like Marcrium Free. Imaging with free Macrium