Prevention tab Where is the info on which direction the prevention tab needs to be on my sdhc card? There is nothing in the package. Its a Platinum 2 sdhc 4gb card

Your camera only can use SD cards. The SDHC is a newer generation of SD cards, that need a different protocol you access the files. The newest version is the SDXC version.
SD cards never exceed 4 Gbyte. The SDHC never are bigger than 32 GD and the SDXC are over 32 GByte.
When you try to buy a SD card, the biggest you will find will be 2 GByte. I own 2 SD cards that have 4 GByte, but even I can't find them on the net any more.
The cards are from Platinum. But I even can't guaranty you the 4Gbyte will work in your camera.

Some firms used to bring out new firmware, as soon as the SDHC cards came out. I succeeded to update my TomTom to SDHC and the old thing now even accepts 16 GByte cards. But Canon did not offer an upgrade for the V550, so you stay stuck to the normal SD cards.

The unit works with SD cards, not with SDHC cards. A microSD card in an adapter behaves like a SD card, while a microSDHC card in an adapter behaves like a SDHC card. There are electronic differences between SD and SDHC that prevent devices from working with SDHC unless they've been designed to.
You're limited to SD and microSD cards 2GB and smaller.

Look at your memory card. SD and SDHC cards have a slide switch along one edge. The position farthest from the contacts locks the card, protecting it from writes. The position nearest the contacts unlocks the card.

The C643 works with MMC and SD cards, not with SDHC cards. You need to go with cards 2GB and smaller.

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.

You can order the manual from
http://shop.nikonusa.com/store/nikonusa/en_US/pd/productID.215420500

There's no SD card in the package because Nikon doesn't know whether you want to use an SD card or an SDHC card, or what brand, or what speed.

You may have the card locked so that the format isn't taking. Verify that there isn't something that is physically preventing the format. If the slide is in the locked position move it to the opposite side.

According to Samsung's page on this camera, the following memory can be used:

External Memory(Optional) : Micro SD (up to 4GB)
Micro SDHC (up to 8GB)

4 GB is acceptable, but I think you do not have the correct type of card. You should be using a Micro SD or "Micro Secure Digital" (up to 4GB capacity) or a Micro SDHC or "Micro Secure Digital High Capacity" (up to 8 GB capacity) card. This is very different from an SD or SDHC card. These Micro cards are very small (smaller than your thumbnail) and are often packaged with an SD adapter card. Regardless if sold with or with out the adapter, the package should say Micro SD or Micro SDHC on it somewhere.

Honestly, it is most likely a defective memory card or not compatible with your camera. Sorry.

Most likely it is not compatable. The SDHC cards are a very different animal to the regular type of cards (which most cards up to 2 GB are). I wouldn't open the package until you are absolutely sure. All info I've found on your camera indicates up to 2 GB (non SDHC only) maximum.