Look for the video card and check if it hasn�t popped out of it�s slot (remember the monitor, the card to which it is connected to is the video card), if so re-seat and try booting up. If the video card is embedded (meaning it is part of the motherboard) it may have failed (sorry, replacement is the only option for this form of motherboard) or if you have a slot for third-party video cards you may purchase one and disable the one embedded within the system.

Note: It is normal for Video Cards to pop out of their slots (AGP or PCI) due to some manufacturers making them with teeny-tiny edges where the contacts are located that fail to seat firmly into the board. They tend to jump out by themselves especially if the PC is used heavily or there is a source of vibration nearby say in an office. The short edges, instead of being grabbed by the connector on the motherboard, sits just above the clamping part which acts as a spring hence the jumping part.