Cant use 4gb sd card in my camera why?

Well, the error literally tells you to format the card. The format function should be in your settings menu. Before you do this, make sure that you've copied all you want off the card and then use the camera's 'format' function to reformat the card. I advise using the camera for the format function because this guarantees the correct file system. If you use your computer to format it, you may easily get the wrong one. However if you need to do it this way, see which file system is currently in use on the drive before you start. Go to "My Computer" and right click on the drive which is the memory card, and choose "Properties". Examples of filesystems are "FAT" (probably FAT16), "FAT32" and NTFS; to make sure your reformat is successful, ensure you use the same filesystem as before.

If this fails, the other possibility is that you've bought an SDHC card and fitted it to a camera that can only accept SD. In this case you bought a larger card for your older camera, not noticing that it was SDHC (or not knowing that it mattered). The new card doesn't work, not because it or the camera is broken, but because it's not compatible.

Cards up to 2Gb are generally SD.
Cards of 4Gb are generally SDHC.
Cards over 8Gb have to be SDHC.

(There are exceptions. Sometimes, manufacturers make 4Gb SDHC cards but some have errors; they disable half of the chip and sell it as 2Gb, but it's still SDHC. 4Gb cards are almost always SDHC because they're cheaper, but 4Gb SD cards do exist. They are so rare that I've even seen a guru on this site claim they don't. I did own one once, but it was very expensive and turned out to be so unreliable that I had to return it. I don't recommend looking for one, because of the problems.)

Your solution is to go find a 2Gb card, and be extra sure that it doesn't say "SDHC" on it.

Usually when you see errors with the card it will be due to a few things. The card is bad or corrupt, the card is the wrong type, or the camera has a fault.

Usually the problem is the card (9 out of 10 times). The cards may need to be formated before use or if they go bad to correct them. If the camera won;t give you the option then try doing this on a laptop or using a card reader and try again. Usually card errors are from bad shut downs or running out of power while taking pictures. Sometimes the card is is dead and won't be fixed by reformatting so you can only replace it. (Don;t toss it as it might work in a laptop).

If the card is too big or the wrong speed some cameras will give an error. Not much you can do about this other than getting a new card. Nothing wrong with the card its just not compatible.

If you have this problem with several cards then the camera itself may be at fault. Unfortunetly that usually means repairing the camera or replacing it. Replacement is usually cheaper.

The Optio S4 works with MMC and SD cards. Your 4GB card is actually an SDHC card. While it fits into the slot, it is electronically incompatible. You need to go with cards 2GB and smaller.

Some cameras can only use SD cards....not SDHC. Check your manual.

The DC-5195 uses SD cards, not SDHC cards. You'll have to buy SD cards, 2GB or smaller.

This is a 6-year old camera. It was not designed to use SDHC cards. Your maximum is a 2gb SD card.

Your problem is that your camera only takes standard SD cards up to a maximum of 2GB. The card you have bought is likely to be a 4GB SDHC model. SDHC is a later development of SD; SDHC compliant devices can still use older SD cards, but SD-only devices cannot use SDHC. This is a hardware limitation so there is no way at all to use an SDHC card in your camera.

Note that if your 4GB card is definitely an SD and not an SDHC then it's still incompatible with your camera: very few standard SD devices were ever made with the firmware and hardware to handle the different memory addressing architecture used by the larger capacity card. Some cameras did have firmware updates to allow the larger SD card to be used, but yours is not one of them.

Your only fix is to sell your card (or keep it for another device) and to buy a regular SD card no larger than 2GB maximum capacity.

I trust that my reply has answered your question fully, please take a moment to rate my answer.

Use a card reader.

this model u cant use more than 1 gb

The A430 works with MMC and SD cards. Your 4GB card is actually an SDHC card and will not work with this camera. You need to use SD cards, which max out at 2GB.