We need to figure out which program is creating all the trouble when booting normally.
There are a couple of different ways to do this, and I believe we are going to need your original XP disk if available.
Lets go through the first steps.
There is a boot method to start your computer with the minimum of services running. The link I am going to give you is to a Microsoft help page for gamers, but it is the detection method we would like to use here. Follow the instructions for the XP based system, and see if we can find which program is bad on your machine.
If you have any problems let me know, I will be waiting for your response.