4GB card won't work in my camera, no memory left message on scree

You need to format new cards in the camera before using.

I'm assuming you tried to format the card in the camera. If there's a firmware update for your camera, by all means, get it.

So far as I am aware, the 5400 will support only up to 2GB cards. As to the firmware upgrade you mention, I don't recall that that has any bearing on the max. card capacity; but it's worth doing for the RAW format support (for me, at least). Cheers and good shooting. Davo, Tas. 

The Nikon Coolpix 4300 only supports the FAT16 filesystem, so it can only support a 2GB partition. To support 4GB you need a FAT32 filesystem.
Put the card in a CF writer and attached to a PC or Mac. Partition 2x2GB partitions, then format them as FAT16. Now put it into the Coolpix 4300 and it should work.

This is because the Coolpix 2100 and 31000 models cannot handle a card of that large a capacity. As it's only a 2MP camera anyway it doesn't need it.

The Coolpix 2100/3100 will usually accept up to a 512MB CF card, and 1GB Lexar CF cards up to and including the 24x WA write accelerated (although write acceleration itself offers no benefits on this camera). With Sandisk only a plain old and now obsolete SDFB allows a 1GB card to be used and the regular Sandisk Ultra (not Ultra II or later) will only work up to 512MB.

The camera was discontinued long before these much larger CF cards were released and Nikon no longer actively support the product so no firmware updates will be available. The hardware wouldn't support such cards anyway.

Compatibility chart for CF cards address below:-

http://nikoneurope-en.custhelp.com/app/answers/detail/a_id/26030/c/241/r_id/127673

4GB requires FAT32. Camera firmware only supports FAT16. 4GB won't work because FAT16 has a 2GB maximum size limitation. 1GB CF card is Nikon's "approved" maximum for this camera.

Catch: 22 1GB -and lesser capacity- CF cards are no longer manufacturered or generally available in 2010. When the current CF card dies, the still working camera also becomes throwaway unless you can source a CF card 1GB or under. 2GB may work, but with 'issues' per caution below.

CAUTION: Anecdotal evidence suggests the final release -& current- firmware for cameras of this generation is also encumbered by with a maximum picture number limitation of 999, realistic at the time of original manufacture when 256MB was a the largest capacity CF card but completely nonsensical now.

Summary: This is my first NIkon Digital camera and also my last.

Apart from the noteriety of the ubiquitous broken Nikon plastic battery latch, a major design flaw Nikon refuse to acknowledge or accept liability to rectify -since self-repaired better than OEM, Nikon policy on firmware support is complete abandonment of product within an unacceptably short service window. ie: a deliberate poilicy of enforced obsolescence.

Suggested Problem Remedy: Do buy a new camera supporting SD Cards of current capacities. Don't buy anything branded Nikon.

Nope, this is not card anymore.

As you know CF is card failure, sometimes this cause to start error 99 , that is lens error , even if there is no problem with the lens.

This happens because the built in software in the camera can get messed up after an error CF.

You fix the problem calling Canon, they will guide through upgrading the firmware in your camera.

First ensure that you are using the camera menu and command to format the new card, and that new cards are properly inserted into the machine.

Call Canon support to get a firmware upgrade.

Hi! I just had the same problem with my Sony A100, when I tried two different CF cards. I was getting the same error message as reported above: "Unable to use card" then "Format?" then that format fails. Thinking the camera is broken, I checked online camera repair sites and also called Sony directly. Sony's flat rate, and that of PrecisionCamera is $228 to fix CF card failure. Then my daughter said, "the CF card in my room works fine in the camera" - and lo and behold - it does. The CF card that works is brand PQI and is marked Hi-Speed 60 2Gb. The cards that do NOT work are marked SanDisk Ultra II 1.0Gb and SanDisk 128 Mb. So my advice is, before you give up on the camera as broken, try a number of different CF cards first.

The second cause of CF failure is if someone has pushed a CF card in the wrong way. That can bend one or more of the tiny metal contact pins in the CF socket in the camera. Look carefully to see that all the pins are straight up. [I don't know how one can straighten these pins, or if the whole socket would need to be replaced...but at least you can determine the cause of the CF failure.]

Best regards - Michael

either the card is not supported or it needs formatting

Try a different CF card, preferably a new one.