This can happen suddenly and without any visible cause. Sometimes your computer begins to load but after some time it stops responding during the start up process. This problem can be caused by many factors.
Your computer could be trying to load windows from removable media. First of all check and remove any CD’s, DVD’s, USB flash drives, memory cards. Remove any digital cameras or external hard drives. Try to restart your computer. If it fails again something else is causing the problem. If your desktop displays an error during start up, this is probably caused by a hardware configuration problem. Your motherboard, CPU, memory or graphic card may develop a problem.