What is the largest SD card I can use? Is there a difference in SD and SDHC?

SD cards max out at 2GB. Make sure you SD cards, not SDHC cards. SDHC cards start at 4GB and go up to 32GB, but they will not work in the NV-GS400.

I beleive the memory that it can read is only limited by the software you are running such as windows XP sp1 and 2 can recognize upto 2gb SD cards but keep in mind that SD cards only go to 2gb anything bigger than that are SDHC and are the same size but designed differently so the reader must be able to read SDHC format. Note if your hardware is capable of reading SDHC cards and your software limits your ability to use anything bigger than 2gb you can still insert and use upto 2gb of space on an SDHC card that is, say 16gb so that is how you can tell if it is hardware or software that limits the use of an SDHC card.

You don't say whether this is a new card or one you used before. I'm going to assume this is a new card (otherwise, it means the card has become corrupted or there is a camera fault).

You say it is an SD card, but don't mention the capacity. "SD" cards larger than about 2GB are actually SDHC cards. SD and SDHC cards fit the same slots, but they are slightly different electrically. Many cameras won't work with SDHC (high capacity) cards. SDHC is not backwards compatible.

I expect your camera just won't work with this kind of card. It is often difficult to find out the maximum capacity memory card a camera will use, as today's cards are much larger that those available when the manual for the camera was written, but as a rule, if the memory size is larger than the largest size mentioned in the manual, you should expect trouble. You can always carry several smaller cards if you really need more space.

I doubt there is anything wrong with the cards. Cards usually come pre-formatted, but you could try formatting them and see if it makes a difference.

However, I expect that your problem is down to compatibility. Many cameras, especially those that are a couple of years old, won't work with SDHC (high capacity) cards. SD and SDHC cards fit the same slots, but they are slightly different. SDHC is not backwards compatible. Unless your camera's manual specifically mentions that you can use SDHC cards, you probably can't. I believe the largest capacity SD card is 2GB. Anything bigger will be SDHC.

The DMC-FZ7 is designed to work with SD cards up to a maximum 2GB capacity (4GB in theory, but very few devices work reliably with the 4GB SD as they simply didn't exist at the time so could not be compatibility tested with most SD devices). You have tried an 8GB SDHC card which the camera is incompatible with.

The SDHC card is the same size and shape as SD but is significantly different "under the hood". SDHC compliant devices can use earlier SD cards, but devices which are not designed to use SDHC cards cannot be updated: the incompatibility lies at the basic hardware level so there is no firmware update to overcome this.

So your guess is correct, but I hope that my reply helps you to understand why. Your fix is therefore to stick with SD cards of a maximum 2GB capacity. As SDHC cards start at a minimum 4GB capacity, you have no risk of buying the wrong model.

Please take a moment to rate my answer.

The camera uses SD memory cards. SD cards max out at 2GB. SDHC cards run from 4GB up, but they cannot be used in SD devices. SD cards can be used in SDHC devices.

The short answer is 2GB.

If your camera is indeed an SD200, am sorry to say an 8GB SDHC will not work in this camera. The camera will fail to recognize it, and will do this by giving various problems as you've run into. The overall problem is that the camera was designed before the SDHC format came out (SDHC cards although the exact same in appearance are different in format than standard SD cards). The largest size card that the SD200 will recognize is a 2GB standard SD card.

Your slot in the iPAQ is a SD slot, not a SDHC slot - therefore it will not read the card. Your PC card is probably a dual reader. The SD cards look the same but are different. Have a read of this...
http://en.wikipedia.org/wiki/Secure_Digital_card

The maximum supported size is most likely 2GB SD Card. Cards with 4GB and more are following a new (incompatible) standard called SDHC (SD High Capacity), SDHC cards work only in devices specifically supporting SDHC. The Optio S5N uses the old SD standard where 2GB are the maximum size.

Omlt the Manual for the particular camera will tell you what its Max capicty is.