I have used Acronis true image in the past with great success, but have not used it yet on my Windows 7 desktop, just with XP installations.
Like many of the better ones, it runs from a bootable cd so you are doing the back-up outside of actually being "in" the operating system.
Be careful if this is your system disk (ie "C" drive) because backing up / restoring the MBR options can vary according to your installation, (ie seperate boot partitions yes or no??). Do it right and all will be fine, do it wrong and your image will not be a bootable one.
I did recently do I disk image back-up from the tools provided in Windows 7 Ultimate. Seemed to work very easily but have not actually tried a restore of such an image as yet.
Might go back to acronis for the next image cause I know it just works.