Good news, I'll try to find this portable version.
By the way, there's a portable version available of Dropbox.
Good news, I didn't know this trick, I thought that it worked only through the installed version, I'll try agait through the web interface.
you can always login to your Dropbox account through the web interface and upload the picture there into your account space and you wouldn't need to use the installed version of Dropbox on your PC
Using the web interface, you will be able to share the link of that uploaded photo too.