For backing up and syncing folders of files I use FreeFileSync. Works great.
But I really need to find a good freeware Windows backup solution that can make incremental system backups. On OS X I'm spoiled by Time Machine. It's simple and yet it works perfectly.
I know Acronis is popular (and I could use the free WD version) but I've heard bad stories about the reliability of the backups it makes. Plus I don't like any tool that installs it's own file system drivers. That can lead to BSODs in certain circumstances.
The Windows backup utility is useless as it requires making a full system image file every time.