When it tells you that, it also says you can choose to schedule a scan at the next bootup. Try that. The scandisk in xp is a lot better than previous versions so there really is no need for norton's. You can still defrag/optimize the disk through norton, which has always been the biggest benefit from using that program at all.
Actually the Norton Utilities 2002 works great! I have used this for several months on my XP machine, and it's so easy to use and very powerful too! Just do as the program tells you and it will work out fine.
Scandisk is dead, long live chkdsk. A different utility altogether, that's why norton's scan disk utility won't work, it's because it can't in the NT environment. Use it all you want in the 9x family, but the NT Family dances with chkdsk.