Here's what I know--

Its a Compaq Presario laptop computer. It will not power up. Battery is dead. Light is on when plugged into the power adapter. I am now letting the adapter stay plugged up in hopes the battery might take some charge. The man it come from says he had someone put a charged battery in it and it still would not power up. Anyone got some suggestions?

If a battery is not just run down but truely dead, it can often prevent a laptop from turning on. Best to remove it and set it aside for the time.
Do anything change when you wiggle the power plug? Do you have a way to measure the actual voltage output of the power adapter? The adapter could be marginal, or the connector could be partly unsoldered.

Of course all of this has nothing to do with the laptop not turning on with a fully charged battery. At that point you're looking at a more serious problem.

Try unplugging it, pulling the battery, lettting it sit for a while, reinstall the battery, then plug the laptop in. That sequence sometimes does it.

A bad battery can keep many units from turning on. It's intentional.

As noted above, unplug it from the power pack, remove the battery, leave it sit a bit, then plug it but leave the dead battery out.

Don't try to force a dead battery to work/charge. Even dead Li-Ion batteries are still potentially dangerous. If it's not charging then either the battery has failed or the system board has.

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Thanks Yall,
I was reading in the Compaq book and it relates the same things yall have said but doesn't say anything about a dead battery causing it not to boot up when plugged into the adapter. Still wont boot with just the adapter plugged in and no battery. The power plug lights up which leads me to think the adapter is working. Probally need to find a good battery to try.