I need a website that can display my 5 megapixel photos in full size or should have an option to download the original file.
All the above mentioned are Good
You could also give Photobucket a try. I believe they host full size (they are resized, but there's a button to show full size). They also offer a free account.
The best option for you is probably Flickr.com since it's free ( up to 100mb a month) and it will store the original sized file ( though it displays a smaller version) and allows for downloads.
In addition to Flickr, you may also wish to consider ImageShack, which allows you to upload unlimited images of up to 5MB for a free account and provides links to see the image in full/download. ImageShack doesn't have a limit of pictures in your collection that you can view, in case you're worried that you can only see your last 200 pictures in Flickr.