Can't format sdhc card in my camera.

The C743 works with MMC and SD cards, not with SDHC cards. While SDHC cards will fit into the slot, they are electronically incompatible. You need to go with cards 2GB and smaller.

There are no 8GB SD cards. Cards this size are SDHC (High Capacity). SD and SDHC cards fit the same slots, but many cameras won't work with the SDHC cards. SDHC is not backwards compatible.

No, it's a hardware issue. Your 8GB card is an SDHC card (the HC stands for High Capacity), but the card reader in your machine is clearly only compatible with the older type SD cards. SDHC devices will accept SD cards, but devices designed solely for SD cards cannot read or format SDHC cards.

There is no firmware update for this, your only fix is to buy an external reader compatible with SDHC cards for connection via a USB socket. Most new readers are fully SDHC compliant, but check the specs for shelling out your hard-earned...

It will take a 2 GB card, I am using one now.
I can't tell you about a 4GB card, but that's a LOT of storage, so you probably don't really need a 4GB card anyhow???

At 4GB size, your memory card is likely a SDHC card, and not a standard SD card. Although they look the same, there is a difference in formatting. Unfortunately your model camera was designed before the SDHC format came out, and it will not work with your camera. But fortunately standard SD cards are very inexpensive these days, and you should be able to purchase a good 2GB standard card for around $6 with shipping:

http://www.amazon.com/s/ref=nb_ss_e?url=search-alias%3Delectronics&field-keywords=sd+card+2gb&x=23&y=20

It will not work with any "sdhc"

i checked specs on that camera and the maximum memory card you can use is 512mb. if you get one that size you should have no errors anymore

Took it to Jessops by the process of elimination "Integral reader faulty."
What a waste of many hours !

If it is still within warranty, return it

According to this site

http://www.sandisk.com/Assets/File/pdf/SDHC%20Compatibility_2007-02-15.pdf

your camera does not support the SDHC cards.