Computer Power comes on, shows compaq first

try replaced memory

Try unplugging everything you can from the computer. Only leave keyboard, monitor, and power cables connected. Then try to turn on again. If computer boots now, then start adding peripherals back one at a time, rebooting each time. when you get the hang, there is your suspect peripheral.

Also, is the monitor itself having issues, or is it the computer? Look at the power light on the monitor, is it staying green, or is turning back to same color when it is in standby state?