OK what you need to do is the following.
1. Go into "msconfig" (every os besides for windows 2000, 95 ,3.x and lower supports it) the way you get there is by going into run and typing in msconfig.
once you are in there the last tab should be startup in there it is best to disable everything even the av software and reboot.
Since all the startup app's arent listed there so after the reboot run a online virus scan such as housecall.antivirus.com there are many more but that's the one i allways use very good.
2.I had nortons and it screwed me over i had so many viruses on my computer chuck that and get bitdefender it has so far served me well you get it at www.bitdefender.com.
Download spybot from www.download.com and scan but i mainly think that there is a virus in his computer and it is killing the anti virus (which nortons is very prone to attack) but it could be spyware as well.
Just ask if you have any questions.