2 ways you can do this
press F8 just before it comes up with the screen STARTING WINDOWS XP - better yet, tap f8 from the memory test till a menu comes up (if it starts loading windows then it didnt work)
select "safe mode" from the list depending on your system setup, this may let you into windows and do what mister two said about deleting norton.
(depending on the way your pc is setup, this may prevent norton from loading when windows does)
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another way is put ur windows xp cd in the computer and reboot, when it asks, boot from the cd.....
once it finishes load, press 'R' for the recovery console, it will take you out to a command prompt, delete norton from there.

if your not familiar with dos type this
cd progra~1 (if progra~1 doesnt exsist, it will be something simular - im doing this from memory)cd symantec
del *.*
type EXIT
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although this wont entirely remove norton (follow mister twos steps) it SHOULD prevent it from loading when you start windows. again, whether this works depends entirely on your PC setup.

(to find the folders on the drive, type DIR)

I take no responsibility for lost data and/or whether your operating system continues to work after the 2nd option. You do it at entirely your own risk. It does work as I have done it myself, but it is rather easy to screw it up with this method, I recoommend you use the first option I gave.