Error 2 in my coolpix 8800. I bought a new battery in the store they said to do that, didn't help an I changed the memory card as well, didn't help

There might be quite a lot of reasons that may cause this kind of format error problem saying memory card not formatted. Check out this article fix memory card not formatted error and learn how to fix it step by step. Best regards.

my Nikon 8800 vr cool pics will not turn on with a new battery but will work on ac

Easy.
Remove memory card
turn on
re-charge
shut down
re-install memory card.....
If it does not turn on with memory card removed, connect to charger and turn on

System Error 2 on Nikon Coolpix 8800 is usually after blow, even the small one, when you or somebody kick the camera and yes, FULL RESET on Set Up mode is just one solution. It's camera's error not the card.

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From Nikon website:

Having a "System Error" message display on the camera's LCD display generally indicates a problem where the camera will need to come to Nikon for repair. A System Error is a general error which can be caused by many things: lens problem, CF Card problem, general camera failure, etc. Before sending the camera in, check these:

1. Use the memory card that originally came with the camera (or a Nikon approved card) [/*]
2. Remove and replace the battery [/*]

If the error is still displayed, contact Nikon's Service Department (below). If the above tips do not help the camera must be sent to Nikon Service, there are no user serviceable parts on Nikon Coolpix cameras.

We apologize for the inconvenience and will do everything we can to repair your Nikon camera as quickly as possible.
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Good luck.

Having a "System Error" message display on the camera's LCD display generally indicates a problem where the camera will need to come to Nikon for repair. A System Error is a general error which can be caused by many things: lens problem, CF Card problem, general camera failure, etc. Before sending the camera in, check these:

1. Use the memory card that originally came with the camera (or a Nikon approved card) [/*]
2. Remove and replace the battery [/*]

Check the memory card. It's probably damaged. If not it should be a software error, and you have to take it to the dealer where you purchased it from

hello. you may be involved in a recall. please read this http://www.nikonusa.com/Service-And-Support/Service-Advisories/COOLPIX-Service-Advisory.page

please rate my answer as very helpful thank you. joe

Genuine Nikon batteries should be available from any camera / photography store.

Batteries Plus stores have aftermarket batteries that are guaranteed to work in your camera for $45. Visit a traditional store or the webpage below to order:

http://www.batteriesplus.com/products/51-0/4803-Digital-Camera-Batteries/282945-Nikon/CoolPix-8800/1.aspx

Hello, Many times when someone fools with a memory card and the camera is on, it sort of backfires when the camera is trying to read or write data to the memory card. Error 10 might be attached to a fault in the memory card or system error. Try doing this first: remove you memory card when the camera is off. Remove you batteries so it can reset. Leave the batteries out for 30 secondsthen replace them. Use a brand new SD memory card and then turn on camera. Go to menu and format the new memory card and see if this helps. Good luck.  

The SYSTEM ERROR 2 problem that is occuring with your camera could be the memory card. Also try cleaning the connections