How to change battery in a All in one zx4931

Re connecting the wires may work without issues.

Unfortunately for you, no. Fortunately for the owner of the password also no.

sounds like a lose wire some were.check mains lead,or what ever you are using to power it up.
somthing is lose some were.

It sounds like the screen backlight has quit working.

Have you tried running check disk? Or if this is a new installation, try reformat the hard drive to eliminate corrupt data.

If you are familiar with BIOS settings, try changing the SATA mode from AHCI to Compatible.

Your cooling fan is probably dead and the system shuts itself off to protect it from burning up the cpu

Sounds exactly like a failing power supply. Hopefully you bought an extended warranty when you purchased the computer. You should look into having the PSU replaced.

The real key to disassembly of the zx4931 is taking the stand off. This is basically a large silver rod, and you'll need to remove it. Start by removing the two plastic covers where the stand attaches to the body of the computer. Press against the narrow portion at the square end of the little cover. This will clear the square-end latch, and you'll then be able to work the cover free.
Once you've taken off the two stand-attachment covers, remove the stand, by unscrewing the three screws at each attachment point.
Now you should be able to separate the black back plastic cover. You may need to run a credit card or screwdriver along the silver edge; in the case of this zx4931 all I had to do was tug gently along the edge to separate it.
Now you're almost in. There are two screws toward what is normally the top of the computer that attach a metal cover over the main workings. With the unit face-down on the table, remove these two screws, then slide the metal cover towards the (normal) top of the computer. That's it! You're in. By the way, those same two screws also hold the hard drive in place.then you will inside battery round as big as quarter coin replace it

My Gateway ZX4931 (purchased 2011) one day just would not power on. I have unplugged it and put it in different outlets, and it still wont turn on. Can anyone help?

Remove standby and / or hibernation from power schemes. They never seem to work correctly. Instead have only the monitor sleep.