The Guardian 'Ask Jack' blog has a great article on the subject: Cloning a Windows hard drive. The Acronis True Image software (commercial) is recommended for disk imaging and for backups. A few free packages are mentioned, which you might want to try. You will typically need to create a bootable CD with these. (You can use blank CD-Rs or DVD-Rs for this purpose.)
However, I'm giving EASEUS Disk Copy (free edition) a go.