The green light on back is on but tower will not turn on, monitor seems to have power! please help!

Please supply the model number of your computer - it's usually on a label on the outside of the case. ... If you have NOT been fiddling with connections inside the case since the computer last worked properly, and you have NOT just changed which ram you have installed, the most likely thing is: Failing power supplies are common and can cause your symptoms. Check your PS. They often partially work, fans and hard drives may spin, leds may come on, yet you get no video and the mboard will not boot all the way. See response 4 in this: http://www.computing.net/hardware/w... Some Compaqs have a BESTEC power supply. If that's what you have that's even more likely