i have a user built pc with windows xp pro.the problem is a few days ago my partner got a registry program and installed it then he updated the windows with sp3 it worked fine at first then when he put it on yesterday it came up saying start windows normally but it would not start so he went through safe mode and took the windows back a few days now every time we try to start windows normally a blue screen flashes and it goes back to start windows normally if try going through one of the others all messages come up and the screen goes black can anyone please help thankyou