computer keeps shutting off as soon it comes on, it's about 5 yrs. Old, and cleaned out all the insides, have any ideas.

So its as soon as it comes on? There isn't a couple minutes or anything?

Where does it shut off, at the log in screen?

no the system will come up and may get to the icons and sometimes it doesn't then it shuts off the monitor, but the green light is on the modem.

You mean the light on the CPU?

Do you mean the whole comp is turning off or just the monitor