If I want to use an image that someone has posted (ex. using Anastasia's ferret/weasel as my computer background--seriously, he's growing on me and I think the message he sends may reflect my work attitude here of late

) what do I need to do to make it all legal and keep the computer police happy?
If you want to use a pic as a background on your computer, that's private use, so just right click on the image, do "save as" and save it to your My Pictures folder. I think you can right click on an image and set it as background from there in Windows? But there's no need to worry about photobucket, etc., in this case at all. Only if you're going to take someone's picture and use it out there on the internet do you need to make sure you follow the rules.
I know there's something to do with the bandwidth thing, I think, and I really am trying to do things right and be legal-er.
That's the linking to pictures that are stored on somebody else's site thing. Let's see if I can 'splain... this is if you want to use a picture somewhere on the internet, like say in a post here. It doesn't apply if you're keeping it for yourself and private (see above for how to do that).
Save the picture to your My Pictures folder.
Upload it to photobucket or similar host.
Get the link from photobucket
Use the link where you want the image to appear. Here on our site, you'd do it this way in a post (but use [ and ] instead of the { and } I'm using below).
Say you found a bear somewhere and wanted to use it in a post here.
1. You would right click the bear image and "Save Picture As" to a file you named bigbear.jpg in your My Pictures folder.
2. Then you would go to photobucket and upload the picture.
Photobucket will give you a URL for the picture, let's say it is
http://www.photobucket.com/sashabear/5467262456/bigbear.jpg3. You come here to FF and make your post. When you get to the place in your post you want the bear to appear, you type this:
{img}http://www.photobucket.com/sashabear/5467262456/bigbear.jpg{/img}
Note: if you click the little framed picture icon in the post tags where it says "Add BBC tags:", it will insert the tags for you, and you can just put the URL in between the two tags.
4. Save your post, et voila, bear in post.
No bandwidth stealing involved! Bandwidth stealing is what you are doing if youlink directly to someone *else's* site instead of taking the extra step to upload it to your own account (e.g. photobucket). Some sites it doesn't matter, but some folks pay for their bandwidth by the MB, and it can add up fast.
Clear as mud?