Count down on memory card

Make sure your new memory card is an SD card. If it's larger than 2GB then it's actually an SDHC card. While it fits into the slot, an SDHC card will not work in devices designed only for SD cards.

The K100D works with SD cards. Your 4GB card is actually an SDHC card. While SDHC cards fit into SD slots, they will not work in devices not designed for SDHC. Apparently your wife's Canon is newer and SDHC-compatible.
The K100D is limited to SD cards, which max out at 2GB.

Actually a 4GB SDHC card should be compatible with an S205, as that camera is new enough to work with SDHC. One thing to try before going through the below linked troubleshooting tips is if you have another card, try it in the camera. If the camera recognizes it, then it's likely that the card you purchased was defective, thus you should return it.

For others reading with similar problems, there are several possible causes for "memory card locked", "memory card error", or "no memory card". The most common is trying to use a 4GB or higher SDHC card with an older camera made before SDHC format came out. Other causes include problems with the tiny slide switch on the side of the card, or the electrical contact switch internal to the camera. The problem may also arise from simple formatting problems if the card has never been formatted in the camera (note that this will also erase the card). Troubleshooting tips for this problem may be found at this link.

You haven't told us what kind of camera it is, but I can guess at the problem. There are two possibilities.

1. Your camera will only read SD cards, not SDHC cards. You've just bought a new memory card, not noticing that it was SDHC. The new cards don't work in your camera, not because they or the camera are broken, but because they're not compatible.

Cards up to 2Gb are generally SD. Cards over 8Gb have to be SDHC. 4Gb cards can be either SD or SDHC, but are almost always SDHC because they're cheaper. (I would avoid the rare, expensive, and problematic 4Gb SD cards.)

Your solution is to go find a 2Gb card, and be extra sure that it doesn't say "SDHC" on it. (If it does, it probably means that they made a 4Gb card, but there were some error locations and so they disabled half of it and packaged it as a cheap-brand 2Gb.)

2. You formatted the card NTFS, whereas the camera needs FAT32. You can format the card using Windows, but there is a complication: Windows defaults to "NTFS" when formatting, but memory cards normally use FAT32. Before you attempted this, you should have connect the card, and checked the 'properties' on the drive that appears. It probably said "FAT32". In this case, you could have gone ahead and formatted the card, but be sure that you chose "FAT32" from the drop-down list. If you format it NTFS, your camera won't be able to read it!

In this case your solution would be to format the card again, but using the FAT32 format.

You might find it useful to check your camera on dpreview (dot) com, and see if the memory card type is shown as just SD or SD/SDHC.

1. Try to format your memory card using a PC/Laptop.

2. Now, insert it in camera and check whether its working!

please rate this advice if it helps....tc! :)

I'm guessing you bought a new 4GB SDHC card. Although it looks exactly the same as a standard SD card, the format the card uses is very different. If your camera is more than a few couple years old, it's likely it was designed before the SDHC format came out. Sorry, but a SDHC card will not work with older cameras.
For older cameras, you'll need to use standard SD cards (usually those 2GB or less). But if you really want to use a 4GB card, do a Google search for 4GB SD "non HC", with the non HC in quotes. Believe Transcend makes one.

I'm guessing you bought a new 4GB SDHC card. Although it looks exactly the same as a standard SD card, the format the card uses is very different. Unfortunately your camera was designed before the SDHC format came out. Sorry, but a SDHC card will not work with your camera.

You'll need to use standard SD cards (usually those 2GB or less). But if you really want to use a 4GB card, do a Google search for 4GB SD "non HC", with the non HC in quotes. Believe Transcend makes one.

The K100D works with SD cards. Your 4GB card is actually an SDHC card. While it fits into the slot is is electronically incompatible.

I have been rummaging around trying to find two solutions: 1) to get my Toshiba Satellite card reader to read SDHC cards and 2) to get my desktop USB ports to read SDHC cards. While MS offers a hotfix for XP, it does not always work because of the different Chip Sets in computers. I have also read where posters say that the SDHC card works in the compter NOW, but NOW will not work in the camera... and the SDHC card NOW works in the camera but will NOT work in the computer.... I found a tekkie article that may help clear the air... SDHC cards are formatted in Fat32x (NOTICE the "x") and SD cards are formatted in Fat32 (no 'x') and these compatibility problems arise when the user unwittingly or unknowingly RE-formats the SDHC card, either when it is put in the computer and won't read or when it is put in the camera and won't read... but just don't bother to mention that THAT is what they did upon inserting the card and only proceeded to complain about an apparent incompatibility. The camera or computer might even mislead you asking if you want to format the card..... but all is not lost. The Panasonic site gives a program AND a pdf instruction book on How To ReFormat an SD or SDHC card specifying the proper Fat32x or Fat32 format. Hope this helps.

I recently bought a DMC-TZ3 and have been researching memory cards. Several sites sell cards with the camera and list the card type. I would suggest buying one of these cards. Any cards larger than 2gb must be SDHC type SD cards. There appear to different types of SDHC cards, 1.0, 1.1 and 2.0. Check out Wikipedia.org for a description. 2.0 cards are not compatable for devices developed prior to 2.0 so that may be the reason for the camera problem. So far I haven't seen anything that states what type SDHC card the camera requires. I found a computer memory site that that sells memory that they say will work. There may be others.
http://www.mymemory.co.uk/compatible-memory/Digital_Cameras/Panasonic/Panasonic_Lumix_DMC-TZ3