Acronis True Image. Always works for me. BUT, I've had it fail once because I had gaps in the image name. Just make sure the image name is just one word.
For example, I imaged my HDD and named the resulting image file as "FULL BACKUP". When I tried to re-image that, it failed. I had saved the image on a nexternal hdd, so took that to another pc, renamed it "fullbackup" and it worked just fine. I hope I don't have to re-image again though, bloody pain.
But also, Acronis can be scheduled to backup important files and data automatically. Which is great, as I always forget to backup manually.