Why does my PC monitor loses signal?

A cable got tangled and mom decided to unplug the Cable that was getting signal for the internet. When we wanted to turn the computer on, it said to insert a windows disk to start the computer and program it. The computer was bought about three months ago so we are upset that it didn't even last a year. If someone knows, please answer.
<config>Windows XP / Internet Explorer 7.0</ config>