It could be your video adapter, but try this
by wpgwpg - 3/26/13 4:30 PM
In Reply to: On bootup monitor goes immediately into POWER SAVE MODE by Patches_1
First, you can unplug the computer & monitor from the EnerSave power bar and plug them into a surge protector or other AC power. If you do it without a surge protector, be sure to pick a time when there're no storms in your area! After testing, you should go back to your normal hookup. If the problem still persists, try booting to Safe Mode and see if that makes a difference. It could be that somehow your display resolution got set to something the hardware can't support. If neither of these things help, you've probably got a hardware video problem.