backup not working

I am running xp pro 32 bit sp3...
xp backup will not complete... whenever i start the backup process the computer completely reboots...
I do not use xp's inbuilt backup system, but I will try to help

have you performed backup before and it worked all right??

if not what steps did you perform in sequence please.

did you back up to an external drive??

This is the first attempt with this machine... I have tried the in-built backup as well as Paragon backup & recovery going to an external hd.. The system reboots in both environments...
First you have got to disable automatic restart on system failure

when system restarts, immediatly start tapping F8, to get to the advanced boot menu, you should see the line Disable automatic restart on system failure, choose this line and press enter.

do you get a blue screen with some stop numbers, and any reference to a file????