I just want to comment on one aspect / misnomer in the original post.

As a general rule, storing pictures on your computer will not slow it down. If you store them on the desktop then yes it is or can slow them down. Also if you are out of hard drive space then not having enough free space will slow your machine down. But if you have a 100 GB HD with 40 GB free, your pictures as a general rule will not be slowing your machine down.

This in now way means don't worry about backing them up, nor does it mean you should or shouldn't remove them from your local HD.