if 擴展名被病毒改變- ACDSEE should be

able to open it.

I believe flickr.com checks the file header when he tried to upload it -- and it is no longer a valid jpg file.

if you don't plan to print it, 一個數碼圖片文件在1-3M之間 is a little bit too large. You can safely re-compress it without much notice at all. You can also resize it. It is not only to save space, but save loading time as well.