Anyhow, how long is a piece of string? there isn't a time it "should take" it depends on how much you are backing up, if you've got a lot of large files it could take a couple of hours at least.
I am backing up because there is an "At Risk"warning from Norton because it has not been backed up.However this has been going on all night now and it has still only completed 24%
You've still not given any indication of how much is likely to be being backed up (do you have a lot of music, pictures or videos as these typically take a lot of space up)
You've also not said what you are backing up to, backing up to an external hard drive will be a lot quicker than backing up to DVD's for example.
Though that said if it's been going hours and it's stuck on 25% I'd be tempted to stop it and try starting again.
I take it you are backing up to the hard disk on the laptop not an outside source.
If this is the case you don't have enough memory to perform the back up. The way to resolve this is to use other media, disks or a seperate hard drive.
I am not a fan of Norton, as I have said on here many times before, it is invasive, time consuming and down right "spiteful".
The free edition of Macrium is good. You can make an image of a computers drive (including operating system). The image can also be browsed so individual files can be copied back or the entire computer can be restored.
Thank you all.I backed up for over two days and it was still only 60%.Then the computer turned itself off and it looks like I have to start over again !