What's the best free backup utility?

After my last near disaster I need to get off my butt and backup this pc. I was using Acronis but the earlier version of it was a lot easier. I don't know if I need to backup sector by sector and that's what I didn't understand.

Is there something that will work the same and would work on boot up, either starting with a separate disk or with the boot up option on the backup disk?

So list any really good backup programs in your opinion and thanks

thanks guys for the suggestions, I will look into both of those

A backup tool that mirrors the files and directories you choose to another file system, like an external hard disk. Different backup jobs can be run automatically on a schedule.

http://www.mlin.net/files/RapidBackupB1.exe

Unlike many I routinely use Windows inbuilt.
I also use Macrium Reflect (free) - I've never heard any serious criticism about it.
Paid Macrium gives extra features for a small outlay.

other free ones that get a mention here
Paragon, Easeus V3.
Free versions of Acronis if you have Seagate or WD HDDs.

Thanks. I'm trying the free acronis ones.