If you could only afford to pay $500 to purchase a digital camera which one would you purchase and why.

After downloading images from my canon g5 camera into my computer via a cardreader I find I cannot open the folder because the file is in ctg format.
What is a ctg file and how do I solve the problem

One of the Canons.
I'm a professional photographer and bought a present for a family member. I spent about $375 on a Canon. I think SD 600 with a 2gb extra memory card. My friend then went three weeks to asia and shot hundreds of photos on that one card. Many digital camera suffer from delay and the Canon is one of the fastest. Many will take the photo too late in candid situations or when you've lowered the camera long after pressing the shutter. Canon also has the best quality.
Fuji is the best at low light situations with great quality at high sensitivity.
The Leica point and shoot also warrants close examination, but it's more expensive.
With the Fuji and the Leica you can do RAW files.
RAW file get processed afterwards in the computer and gives you a latitude on density and color. Most of the others are processed inside the camera and delivered as jpgs which is a compressed format that is now locked in as to color and density. It can also give you some issues with banding in skin tones and skies. Jpgs are also not as good if you like to do your own photoshop processing afterwards and perhaps make big prints.

Short answer: Canon or Fuji FinePix E900 about $250 with extra memory.

The next step is more expensive and usually heavier, but more capable. A used Fuji S2 is a dSLR and heavy to carry around, but will take great photos for $250 plus a lens.

Mike 33: your answer is really a question and the answer is to install the software on your computer that came with the camera or download from their website. Photoshops Raw converter may be able to read the files, but it is a proprietary file format.

Good luck to you both