My system won't start.

This can be for a number of reasons including software corruption or hardware failure.

If the system won't turn on and you have checked the power to the system, you could have a failed power supply. This will need to be replaced.

If the system powers on but won't enter Windows, you could try starting in "Safe Mode". If the system enters Windows under Safe Mode, you probably have a software issue. This could be anything to a Windows issue or a recent driver or software loaded onto the system causing the issue.