Norton NIS 2010 so dreadfully slow for first 30 mins.........Help!

I used to have NIS 2009 on my pc which has XP pro OS and I found it great. I bought NIS 2010 , used the norton removal tool for 09 version and installed . Now the boot up is taking about 8 mins before I can use my pc :mansurprised: The cpu is showing about 8 % usage yet the hard drive light is running constant. It stays like this for about another 20 mins and the pc is dead slow and stop. Then things settle down and the pc is fine to use. I also have netnanny on my pc if that has any relevance, btw it didnt interfere with NIS 2009. NIS 2010 is making using my pc a chore and its a pain not being able to use it for 30 mins after switch on, strongly considering taking it off , can you offer me any advice please ?