Compaq Presario 7470 start up

A few days ago, my pc stopped going online. I checked out the network adapter and it said one wasn’t installed. I removed it from the device manager and ever since then when I try to turn it on, the green light on the tower comes on, but the monitor light turns green to amber as if in sleep mode and I get nothing. I haven’t switched any cables and I checked all the connections, nothing has changed. What should I do?