Is there a good DVD burning/backup software that is free?

What operating system?

For Macs, I'm in love with disco, which is not free, but is cheap-- http://www.discoapp.com/

How about for Windows?

I really like CD Burner XP pro. You can find it on www.download.com. Look under "Audio & Video" then "CD & DVD" burners. Totally free. I use it a lot, no problems. The CNET editors seem to like it too. I use it for backups, burning iso images, lots of stuff.

Oh, not nag screens or anything annoying either.

If you're looking for a more mainstream program, Nero Burning ROM is pretty fantastic. It's attainable illegally for free, though it's also not all that expensive, comparatively. I like the newer versions a lot, and it'll do pretty much absolutely anything. The only thing it won't do, really, is rip copies of copyrighted DVDs.. but not a lot of regular burning software will. For that you'd need a different program, most of which you can get for around 30 bucks, or, again, illegally - like most things on the internet.

I second Nero Burning ROM -- the 2nd best thing to buying a Mac =)

yes there are many
at http://downloads.com youcan d/l for free

yes there are many
at http://www.downloads.com youcan d/l for free

Also for converting DVD’s take a look at VLC.

Also, I believe handbrake has been released for windows
http://handbrake.fr/

But VLC is it for me!!